Some of these are also applicable to Unfair Stamp or Judge.
Early-game, you can use Iono as a draw Supporter if your hand is really bad, or if you managed to play most of it. However, Iono also affects your opponent, so if your hand is passable but your opponent seems like they're bricking, don't feed them a fresh hand!
Good times to Iono your opponent are after they've taken a KO, or after they search for a card but do not play it on the same turn.
For maximum card advantage, you'll want to save Abilities that draw you cards/Prizes (e.g. using Munkidori to KO something at 30 HP) for AFTER you Iono. If you have Abilities that feed your opponent Prizes (e.g. Dusclops/Dusknoir), you'll want to use those BEFORE you Iono.
In the early game, if you naturally draw into Technical Machine: Evolution and the only copy of a particular Stage 1 in your deck, you can prepare the TM and Energy on your Active first, then use Iono to put the Stage 1 back into your deck so Evolution will be able to find it.
In the mid/late game, if you have useless Items like Buddy-Buddy Poffin in your hand, play them for no effect before Iono-ing. This stops them from going back in your deck after you Iono, so you won't draw into them again later. The same goes for Technical Machines, as they discard themselves at the end of the turn.
Iono bottom-decks the cards that were in your hand, so if your deck is still relatively large or if you lack draw power, you are not seeing those cards again soon. If you need those cards back, search effects (Artazon is a common one) can give you a chance to redraw into them, since you always shuffle after searching your deck. Conversely, if your hand was dead but your opponent was kind enough to Iono it away, refrain from using effects that shuffle your deck.
When you Iono your opponent low, often their best response to dig out of it is using Fezandipiti ex to draw 3 cards. You can counter this by KOing their Fezandipiti ex (using Counter Catcher to drag it in, since you're using Iono as your Supporter for the turn), though note that if they have Night Stretcher, they can just get Fez back. Alternatively, you can attack without taking a KO — Dragapult ex can do this while still making progress towards future KOs with its spread damage — or you could attack with a retreat locker after Counter Catcher-ing in a liability.
Against opposing Ionos, try to space your outs so you have one copy in hand and the rest in your deck (i.e. don't go searching for a second copy to add to your hand). That way, if they don't Iono you, you can play the out in your hand, and if they do Iono you, you have a better chance of drawing into one of the remaining copies in your deck. Example: if you have a Boss's Orders in hand which will win you the game next turn, and you play Pokégear 3.0, don't put another Boss's Orders in your hand with it. Leave the extra Bosses in your deck so you can draw them if you get Iono-ed.
If your opponent has 1 out to win the game (say Boss's Orders) and you've just survived a turn without them using it, don't Iono them. Since they did not play the out, you can deduce that they don't have it in their hand, so Iono-ing them would just dig them closer to it.
If you're playing Professor's Research as your Supporter for the turn, and also have an Ultra Ball with enough discard fodder for it, always use the Ultra Ball before playing Research, since you're going to discard those cards anyway. Obviously, you can get a useful Pokémon with Ultra Ball and play it immediately, but if you don't have any Pokémon that you want to play, you can Ultra Ball for a dead card that you won't need for the rest of the game (like a Squawkabilly ex past turn 1) before discarding it to Research to thin your deck.
Deliberately searching for and discarding an Evolution even though you can't evolve into it yet is also an option if you have 2 or more Night Stretcher in your deck. Say you still have 2 Stage 2s, 2 Night Stretcher, and 3 Ultra Ball in your deck. Your hand has the 4th Ultra Ball, 2 discard fodder for it, and Professor's Research. If you Ultra Ball for a Stage 2 and then play Research, you have 6 outs for getting a Stage 2 into your hand (1 Stage 2 left in your deck + 2 Night Stretcher to recover the Stage 2 you discarded + 3 Ultra Ball). If not, you have 5 outs (2 Stage 2s left in your deck + 3 Ultra Ball).
If you have access to both Squawkabilly ex and Carmine/Research in your starting hand, use the Supporter before Squawk and Seize. If you Squawk and Seize first, there is no guarantee that you will draw into another draw Supporter to continue ripping through your deck.
You don't have to play Research or Carmine if your hand and board are already as good as they can be. It may be tempting to do so if you're low on cards in hand, but the key question to ask yourself is "will playing this Supporter improve my position?". If you need to draw into more pieces, then go ahead and play it, but if your board state is already amazing (e.g. 2 attackers fully powered up and a Boss's Orders in hand), it doesn't matter if your only other card in hand is Research, you do not want to play it and throw away the Boss's Orders that you're already holding.
Ultra Ball is Mew ex's best friend, as it can act as a discard outlet to dump useless cards from your hand and get you under 3 cards for Restart. It even searches out Mew ex if you don't have it! Earthen Vessel is similar, but discards only 1 card. Remember that you can choose not to get anything with Ultra Ball or Earthen Vessel, or get only 1 Energy with Earthen Vessel.
Try to leave a Bench slot open so you can play Nest Ball or Buddy-Buddy Poffin to reduce your hand size if you draw into them.
If you have access to both Mew ex and Fezandipiti ex, use Restart before Flip the Script. If you Flip first, it will be difficult to reduce your hand size again for Restart.
If you have 1 Rare Candy and both Pidgeot ex and the Stage 2 form of your attacker in hand, Rare Candy into Pidgeot ex, then use Quick Search to get another Rare Candy for the attacker. If you Rare Candy straight into the attacker instead, you'd be stuck with a dead Pidgeot ex in hand.
Similarly, if you have 2 Rare Candy and an Ultra Ball, you'll want to Ultra Ball for Pidgeot ex, then Quick Search for the Stage 2 attacker, instead of Ultra Balling for the Stage 2.
Instead of Quick Searching for a particular card directly, you can Quick Search for another card (Supporter or Item) which in turn searches for that card. For example, if you need an Item like Rare Candy or Counter Catcher, you can Quick Search for Arven, which you then play to search for that Item plus an additional Pokémon Tool for value. If you need an Evolution Pokémon, you can Quick Search for Jacq, which will get TWO Evolution Pokémon, or Arven → useless Tool + Ultra Ball (+ 1 more discard from hand) → Pokémon. If you need a Basic Pokémon, you can Quick Search for Buddy-Buddy Poffin or Nest Ball to thin your deck of those cards.
In the late-game, if you need a 2-card combo to win next turn and already have one of the pieces in hand, spending your Quick Search on a useless card this turn is ironically the best play. Let's examine what would happen based on 1) whether you Quick Search for the other piece or a useless card this turn, and 2) whether your opponent Ionos you on their turn. Assume your opponent doesn't have a way to stop Quick Search.
If you Quick Search for the other piece and they don't Iono, you win. Just play both pieces.
If you Quick Search for the other piece and they Iono, you probably lose, because both pieces are now at the bottom of the deck and you don't have enough draw/search power to get both.
If you Quick Search for a useless card and they don't Iono, you win. You're already holding one piece of the combo in hand, so just Quick Search for the other and play them both.
If you Quick Search for a useless card and they Iono, you can still win if Iono draws you into the piece that was missing. If that happens, Quick Search for the other piece that was bottom-decked and play them both. Note that Quick Searching for the useless card thins your deck slightly and makes it more likely for you to draw into the missing piece, which is why you do that instead of declining to use Quick Search for that turn.
So, if they don't Iono you, you win either way, but if they Iono you, you are more likely to recover from that if you had Quick Searched for a useless card.
Bread and butter combos:
Buddy-Buddy Poffin + Technical Machine: Evolution gets 2 Stage 1s into play, provided you can spare an attack (and also have the Energy).
If you're going for this line, you'll need to make sure that six cards (Poffin, TM: Evo, first Basic + Stage 1, second Basic + Stage 1) are in your deck and you didn't Prize all copies of any one of them. You can check for all six cards during the Arven search, moving each card to the front of your deck as you find them, and change your Arven targets if you realize any one is missing. If you are playing in Japan, though, you are not allowed to rearrange your deck during searches, and should instead push the cards up so they stick out above the other cards in your deck.
Buddy-Buddy Poffin + Air Balloon lets you search for a 0-Energy attacker like Budew or Cleffa and retreat your starter into it (provided it has a Retreat Cost of 2 or less). This is usually the backup plan for setting up if you can't use TM: Evo for whatever reason (don't have Energy, or Prized the TM/Stage 1).
Nest Ball + Technical Machine: Turbo Energize lets you search for Cornerstone Mask Ogerpon ex and attach 2 Energy onto it. This is the go-to play if your opponent's deck is walled by Ogerpon.
Secret Box searches for one Trainer card of each sub-type. You can play Arven, search for Secret Box + a useless Pokémon Tool to use as discard fodder, then discard the Tool and two other cards in hand for Secret Box. This sequence effectively turns the two other cards into a Stadium and a Supporter, on top of what Arven would normally get you on its own (Item and Pokémon Tool).
If you need to flood the field with Basic Pokémon, Secret Box can search for Buddy-Buddy Poffin + Artazon to put three of them down.
Generally, it's safe to discard something to Secret Box if you know you're going to get another copy of it off Secret Box. Some examples are discarding Buddy-Buddy Poffin to search for another Buddy-Buddy Poffin, discarding a Basic Energy to search for Earthen Vessel or Night Stretcher, or discarding Supporters in general (since Secret Box will find you a new Supporter anyway). Though if you play a card as a 2-of, you should check whether the other copy is in your deck with another search effect before discarding it — you don't want to discard a Technical Machine to Secret Box only to discover that the other copy is Prized, for example.
Several Items convert Arven's Item search into other types of cards:
Nest Ball searches for high-HP Basics that Buddy-Buddy Poffin can't get, e.g. Munkidori, Fezandipiti ex.
Energy Search or Earthen Vessel searches for Basic Energy.
Ultra Ball gets any Pokémon, usually an Evolution in the midgame when you can't spare an attack for Technical Machine: Evolution. Getting a useless Pokémon Tool (like aforementioned TM: Evo) with the other half of Arven partially pays for the discard cost.
Rare Candy accelerates a Basic into a Stage 2. If you have the Basic down and draw into the Stage 2 naturally, you can Arven for Rare Candy to turbo it out. If you draw into Rare Candy naturally instead, then you Arven for Ultra Ball for the Stage 2 and turbo it out all the same (minus two cards for Ultra Ball).
Night Stretcher gets any Pokémon or Basic Energy from the discard pile. You can use it to get back an attacker, or a Fezandipiti ex that they KOed thinking it would limit your draw power.
Counter Catcher or Prime Catcher replicates Boss's Orders' functionality.
Pokégear 3.0 digs for a Supporter on your next turn.
ALWAYS CHECK THAT YOU HAVE A TERA POKÉMON IN PLAY BEFORE PLAYING NOCTOWL. Overlooking this is the fastest way to throw the game, especially in Flareon ex where the Eeveelutions are Teras, but the non-ex Eevees are not. Don't get fancy thinking you can play your Tera later during the turn to make your opponent guess whether you had it in hand all along or drew into it along the way. Put the Tera down before you forget.
When you use Fan Call, you want to have only one Noctowl (or Ultra Ball) in your hand afterward. You usually only want to play one Noctowl per turn anyway, and more importantly, keeping the other Noctowls in your deck gives you more chances to draw into another one if you get Iono-ed. If you're using Ultra Ball as a facsimile for Noctowl, you can Fan Call for the other Fan Rotom (to use as discard fodder) instead of Noctowl.
If you are missing both Fan Rotom and a Tera on T1, but only have one Nest/Ultra Ball, it's better to get Fan Rotom first. If you whiff the Tera on T1, you can always hope to topdeck it on T2, but if you whiff the Fan Call on T1, the opportunity is gone; you can't use it if you topdeck Fan Rotom on T2.
If you play Buddy-Buddy Poffin as well as the 80 HP Hoothoot in your deck, you'd want to get the 80 HP Hoothoot off the T1 Fan Call, so Poffin can get the other 70 HP Hoothoots later in the game.
If Area Zero Underdepths gets bumped and you have to discard Pokémon from your Bench, Fan Rotom and Noctowl are obvious choices. Discarding Noctowl gives you the option of turning a topdecked Night Stretcher into Noctowl to evolve any Hoothoots on your Bench. If you still have Professor Turo's Scenario, however, you might want to keep 1 Noctowl around so you can Turo it and evolve a different Hoothoot.
Against Dragapult ex, they can brick you by using Hawlucha to ping your 70 HP Hoothoot and finishing it off with Phantom Dive's spread, leaving you with no Hoothoot to evolve going into your turn. Try to save the 80 HP Hoothoot (evolve the 70 HP ones first) as a countermeasure against this.
If your opponent goes first, starts with a <= 70 HP Basic in the Active, and plays Artazon, you can punish them for it by using Artazon to search for Fan Rotom, switching/retreating into it (you should have Latias ex for free retreats), attaching an Energy, and using Assault Landing for the KO.
Ditto is not a hard once-per-turn. If you happen to start with Ditto in the Active and have Night Stretcher in hand, you can use Transformative Start, Night Stretcher Ditto back and Bench it, then retreat to Ditto and use Transformative Start again. Latias ex and Mew ex retreat for free, so they are good targets for the first Transformative Start.
Bread and butter combos:
Crispin + Sparkling Crystal/Energy Switch accelerates your attacker from 0 to 3 Energy. Energy Switch only works if you already have an Energy on board, which means having attached the turn before, or using Teal Mask Ogerpon ex's Ability.
Crispin + Nest Ball searches out and powers up any 2-Energy attacker, like Terapagos ex or Lillie's Clefairy ex.
Area Zero Underdepths + Buddy-Buddy Poffin expands your Bench and lets you put down 2 more Hoothoots. In Flareon ex, Cyrano can replace Buddy-Buddy Poffin for the purpose of filling your Bench.
Ultra Ball for Mew ex lets you dump the rest of your hand and draw back up to 3.
Nest Ball for Fezandipiti ex converts a Trainer search into 3 cards after you've taken a KO.
A lot of mobility cards (Prime Catcher, Professor Turo's Scenario, Air Balloon, Switch) are searchable off Noctowl. In particular, if you play Iron Leaves ex, you can go Noctowl → Ultra Ball → Iron Leaves ex.
Counter Catcher + Briar wins you the game when you're down 3-2.
Nest Ball (for Bloodmoon Ursaluna ex) + Boss's Orders wins you the game at 2-2 if you have an Energy to attach.
Try to hold off taking KOs with Adrena-Brain until you absolutely need to. KOing a Pokémon with 30 or fewer HP remaining can simplify the board state, but keeping it alive lets you extract more value from Counter Catcher and Iono, as well as leave your opponent with less Bench space to work with. Munkidori decks typically have good spread/snipe on their other Pokémon; this is something you'll have to get used to if you play those decks: keeping the board state complicated, staying behind in Prizes, and taking 3+ in one turn when the time is right.
Energy Switch or Professor Turo's Scenario/Penny can be used to get multiple Adrena-Brain activations if you only have one Darkness Energy or Munkidori, but multiples of the other. With Energy Switch, you activate the first Munkidori's Adrena-Brain, then Energy Switch the Darkness Energy onto the other one. With Turo/Penny, you activate Adrena-Brain, scoop up the Munkidori, then replay it, attach Darkness Energy, and use it again (it counts as a new card after it's left the field).
When you have 2 charged Munkidori in play, Turo/Penny lets you move 90 damage to their Bench, enough to KO most evolving Basics/Stage 1s.
Aim to 1HKO your opponent's Pokémon. If you merely leave them damaged, they can fling the damage back at you. If you can't KO their Active, consider Bossing something else in to KO (like the Munkidori!), or even not attacking.
This is why it's important to refrain from using weak attacks for chip damage early-game if your opponent could have Munkidori. Is the chip damage going to help you hit a 1HKO, or is it going to help them hit a 1HKO after they drop Munkidori and Adrena-Brain the damage over?
If your opponent has something that can generate damage on their side of the board (Froslass, Gardevoir ex), try to go after that Pokémon. (Going after Gardevoir ex is a good idea anyway, as it also accelerates Energy.)
Avoid putting 30 HP Pokémon (Budew, Cleffa) into play, as they make for really easy prey. If you play Joltik, you'll have no choice but to play it into Munkidori, but sometimes this doesn't matter: you can charge up an Iron Hands ex and Boss KO their Munkidori to remove the threat, or you can maintain a board of 2-Prizers to force your opponent to go 2-2-2 and ignore Joltik, or you can 1HKO every time you attack so your opponent doesn't have any damage to Adrena-Brain back. Evolving Joltik can bring it out of Munkidori range, but it will no longer retreat for free under Latias ex. (That shouldn't be a problem though, as you should have an Energy left over from meeting Jolting Charge's Energy requirement that you can use to retreat, or you can attach Air Balloon to Galvantula.)
If you have Munkidori, but are not the Munkidori player because your opponent has more of them than you (or they have spread attacks, which make their Munkidori deadlier), use your Munkidori defensively by moving damage onto Pokémon that you're going to KO when you attack (even if it's overkill and you'd already KO without Adrena-Brain). Putting the damage counters on something that's going to die denies your opponent that resource.
Cursed Blast feeds your opponent a Prize, so think about whether you'll have the opportunity to actually use it before benching Duskull. If your opponent is down to 1 Prize, Duskull obviously becomes useless. Worse is if you've already evolved Duskull and your opponent goes down to 1 Prize — now they can Boss Dusclops/Dusknoir in and keep it trapped there; it can't escape by blowing up because that would lose you the game, and it can't feasibly retreat because that costs 2-3 Energy. At higher Prize counts, you'll have to think several turns ahead to determine whether there will be a spot where you can use Cursed Blast.
Giving up a Prize with Cursed Blast can often turn out to be beneficial, as it may turn on Counter Catcher or Briar, and Iono will leave the opponent with fewer cards in hand.
If you're going to use both Cursed Blast and Iono in the same turn, use Cursed Blast first, as Iono will then bottom-deck the Prize they took. Doing it the other way around translates to them having 2 more cards in hand, which is pretty significant!
Cursed Blast is not a hard once-per-turn. While your deck may only run 1 copy of Dusknoir, if you already have it in play along with a Duskull/Dusclops ready to evolve, you can pop the Dusknoir, Night Stretcher it back to hand (or Super Rod it into the deck and search it out), evolve the Duskull/Dusclops into Dusknoir (using Rare Candy if Duskull), and pop it again.
A good rule of thumb to avoid getting stuck with only 1 type of Basic Energy in your deck is to prioritize taking Energy that you have the most copies of with Crispin. In Tera Box for example, Grass is your most plentiful Energy, so you'll often get Grass + something else with Crispin. In Joltik Box, it can be correct to leave the lone Psychic Energy in your deck for a future Crispin, even if you know that you won't be attacking with Lillie's Clefairy ex (and thus the Psychic Energy would be functionally Colorless). (It depends on what attackers you need for your Prize map; if you need Pikachu ex to take the last 2 Prizes, keeping Psychic Energy in the deck wouldn't be useful, but it might be if you need something else with Colorless in its attack cost instead.)
When you start running low on Energy in your deck, you might have to change your sequencing to lower the risk of not having 2 Energy for Crispin. Getting stuck with 1 Energy in your deck is incredibly bad, as Crispin only attaches for free if you have the second Energy. Some examples:
If you're down to 2 Energy in your deck and have a Fezandipiti ex activation for the turn, play Crispin before using Flip the Script. If you Flip first, you risk drawing into an Energy.
If you play Earthen Vessel to find an attachment for this turn and notice that you have 3 Energy left in your deck, and also need to play Crispin next turn to win, you'll want to take only 1 Energy with Vessel, leaving the other 2 in the deck for Crispin.
Super Rod can put Energy back into the deck for Crispin.
If you're playing a deck which needs to assemble a combo of a Basic and an Evolved Pokémon (e.g. Brute Bonnet + Conkeldurr, or Ethan's Ho-Oh ex + Armarouge), and are missing both Basic forms and only have a single search (e.g. Nest Ball or Artazon), use it on the evolving Basic. This is the only route with a glimmer of hope — if you topdeck the other Basic and the Evolution next turn, you're still in the game. In contrast, if you spent the Basic search on the non-evolving Basic, it doesn't matter if you manage to draw into the other Basic + Evolution next turn; since the evolving Basic hasn't been in play for a turn yet, you can't evolve it immediately, and will fall even further behind.
If you have an Ultra Ball and are missing two Pokémon for a combo (e.g. you have Timburr down, but are missing Brute Bonnet and Conkeldurr), don't use the Ultra Ball immediately. Wait a turn to see what you draw into before using Ultra Ball to find whichever piece you whiffed: if you drew into Brute Bonnet, then you'll Ultra Ball for Conkeldurr, and vice versa. The exception is if you think you're going to get Item locked, in which case you should use the Ultra Ball before it becomes a dead weight in your hand.