You don’t need to specifically follow all of these tips if you are aiming for a specific theme or gimmicks, but these are recommended to keep in mind.
This step is only recommended if you are a newbie. This helps you get a good grasp on the mechanics of the game, as well as gimmicks and other tricks that you can use.
This will help you visualize your chart and give you an idea on how you want your chart to be, what difficulty, and your main focus of the song. Granted, you may change your vision of your chart midway, but it gives you a base to start off with.
A common trap nowadays is that people would put a lot of obstacles in your way in certain games that have level makers, like Geometry Dash, Mario Maker, etc. You don’t necessarily need a bunch of notes to make a level hard. You don't need to force your player to spam 16 notes in one screen. If you find yourself placing too much tap notes, you can instead utilize the different types of notes to make it difficult and less spammy.
An extension of this tip is to not capitalize on every note of the song by placing a note there. Choose which instrument(s)/vocal(s) you want to focus on, not all of them (Unless there is only a few in a part of a song).
The following points may vary depending on the song’s BPM, time signature, genre, etc. you are charting.
Typically, most songs are charted with a scan line speed that is equal to double of the main BPM. (In PCtyx, this is calculated somewhat differently)
If a song has a high BPM like 400, it's recommended to not double the BPM value.
If a song's scan line speed is still too slow for your chart after doubling the value, try doubling it again.
If you are charting speedcore, god bless all of us.
What this means is that the chart should adhere to the players’ experience and the chart’s declared difficulty. Basically, don’t spike the difficulty out of range in the middle, make it possible for players at their “current stage of the difficulty” to clear the song, etc. In short: don’t be a dick.
If you need to increase the difficulty due to the song’s melody, consider changing the difficulty number.
Most importantly, make the chart possible to fully complete, even if you aren't an expert.
For lower-difficulty charts, position your notes so they they are able to reach them without moving their hands too fast.
Cytus and Cytoid is basically DJ MAX but only one screen. That means overlapping notes block vision of other notes. Not only does this make it hard to execute, it is also incredibly frustrating. Avoid overlapping notes as much as you can (A little overlap is OK, as long as it doesn’t obstruct a note too much)
This lets you test out your chart(s) and spot any problems, whether they might be misplaced notes or unexpected bugs. Play it more than once to iron out any problems if need to.
If you can't beat your chart, and you are not a good player, you may ask someone to playtest it if you are not sure if it is possible to beat.
If you intend to troll your players, you are a demon masochist. Why are you making yourself suffer?
Rate your chart appropriately from 1 to 15+ (1~16). Look at charts on the featured section as a reference. Ask reviewers on discord to review the difficulty for you if you're having too much trouble determining the difficulty. Failing to rate a chart properly will have consequences. Ask yourself these questions:
Is the chart suitable for what the difficulty tells the player?
Is the chart a troll, impossible to play, or have too many glitches and bugs?
If this is the case, change your difficulty value to a decimal. This will list your chart as a "troll" level, or a level that will not affect a player's rating.