Opening Leads is one of the more difficult subjects in bridge. I am definitely not an expert on this subject matter. However, for the beginner or intermediate (who has no particular learning on this topic), even a small amount of guidance can probably do a lot of good. Within a 24 board tournament, even if your use of the technique described herein, results in a better result in a couple of boards, this merits some effort.
Hence, in this document, I will make a simplified description of the opening lead.
How to make an opening lead can be divided into 2 sections.
Choosing a suit to lead in trumps. For now, I will leave choosing a lead in NT alone except for a brief mention.
Choosing a card in the suit to lead to give information to partner (this is easier).
I will also introduce a simple carding method. This is where you use card play to signal information to your partner in defense.
As per introduction, the opening lead can be divided into choosing a suit, and then choosing a card within the suit to give information to partner. This is the easiest bit to describe. Here it is as follows:
A lead of a low spot card implies the leader has a honor in the suit and encourages a lead back. In NT contracts, this is usually 4th best.
A lead of a high spot card implies the leader has led from "top of nothing". The cards may be anything from a doubleton to a longer suit.
A lead of an honor (AKQJ) implies there is a touching card in the sequence (e.g. a lead of a K implies leader has a Q). This includes interior sequences like leading a J from KJT4.
A lead of an honor may ocasionally be the lead of "top of doubleton". Most commonly, if the doubleton is Ax (leader will void his suit by 2nd trick) or if the leader is leading to a suit that partner had bid.
The partner of the leader will need to combine this information with other information, such as :
How strong his partner probably is (from the bidding)
The layout of cards in his hand and in dummy.
The distribution and strength of cards in opponents hands (from the bidding).
In general, points #1 and #3 probably imply that at some point in time, he should lead back in this suit. If the bidding was competitive and he had bid the suit being led, this more strongly suggests that.
Even #2 is useful information potentially. It suggests a suit to avoid (unless of course he thinks partner has little strength to begin with).
#3 and #4 may be confused together. if in doubt, assume #3. But do use clues from the bidding.
In NT contracts, it is common to lead 4th best from a 4+ cd suit.
In such a case, both defender (partner of the leader) and declarer might want to apply Rule of 11 to try to work out what might the other hidden hands hold. Obviously, defenders also have access to view dummy's cards.
I will not describe it further but provide a reference, as this is not the main focus of this page : https://en.wikipedia.org/wiki/Rule_of_11
It is suggested you don't do the following:
Do not lead from a holding such as Axx or Axxx. If opponents have a singleton, your ace might become useless.
Do not lead from a suit with broken honors. Such as KJx, AJTx etc. The declarer is on your right - these suits are better suited to catching opponents high cards.
Avoid leading opponents bidded suits. If you must, choose one that dummy has bid.
You might want to lead the following:
A suit that your partner has bid. (this is high priority)
A singleton (also high priority).
A doubleton (lead top of doubleton) ONLY if (A) it is a suit your partner bid, or (B) it is Ax (you will be void on your second lead).
Lead a suit where you have a sequence (KQxx for example).
Lead a trump if you believe you or your partner has lots of them.
Lead a trump if your other side suits are not appealing and/or opponents have bid multiple suits to arrive at a trump contract (suggesting a shortage somewhere).
IF ALL ELSE SEEMS UNLIKELY, make a passive lead. An unbid suit in which your cards are useless, or a suit which you think will lose a trick safely (not give a ruff to opponents).
As usual, it is a high priority to lead to partner's suit (even if you only have a doubleton or 3 cards).
You should avoid leading opponents bidded suits. If you must, choose dummy's bidded suit.
Lead your best suit, unless you are leading to your partner's bidded suit (or a suit you believe partner has length in).
If you have very few points, try to guess your partner's best suit and lead to it (even better if he bid it - see #1).
It is ok to lead from a holding like Axxx or Axx (this is the opposite of the advice for trump contracts).