Source: ACBL
Someone comes up to you and gives you an opening lead problem.
This is your hand: 
9 7 6 
A 7 6 
9 2 
Q J 8 5 2
What do you lead? You can make a case for just about; anything, but; it would be nice to know the bidding and the contract. To satisfy that need, I am giving you four different auctions. You are West No one is vulnerable.
1)
| West | North | East | South |
| Pass | Pass | 1 |
|
| Pass | 2 |
Pass | 2 |
| 3 |
The End |
2)
| West | North | East | South |
| 1 |
1 |
||
| 2 |
3* |
The End |
* weak
3)
| West | North | East | South |
| 2 |
2 |
||
| 3 |
Pass | Pass | 3 |
| The End |
4)
| West | North | East | South |
| 1 |
|||
| Pass | 1 |
Pass | 1 |
| Pass | 1NT | Pass | 2 |
| Pass | 3 |
The End | |
Answers
1. This is pretty easy. There is little reason to lead spades or diamonds, s0 your choice must be a heart or a club. A rule I tout with passion is that you do not lead or underlead aces against suit contracts. If you have A-K-x, you can lead the ace, but not otherwise. Even if partner has bid the suit, leading an ace is way down on the list of desirable leads. Lead the Q. No second choice here .
2. On this one, the issue is whether to lead partner’s suit (hearts) or something else. I offer this hand as an example of how far I will go to avoid leading a suit headed by the ace. Even with partner’s heart bid, leading this suit can be a disaster.
Your partner bid 1, but he can have all kinds of holdings that do not include the king, ranging from 10 9 54 3 to Q J 103 2. If you lead this suit, declarer will have the king much of the time and he will get a free trick. You have a much better choice in the Q.
3. Partner bid hearts strongly. I can accept the A but I maintain that you should not be surprised if it does not work. Some of this depends on your requirements for a weak two bid. I am happy to open 2 with Q-10-9-8-5-4 so for me,
leading the A won’t be a lock. If your requirements are higher, then lead a heart.
4. This is an acceptable moment for a trump lead. Their side has stopped in a partscore and you can see that their main side suit, clubs, is breaking poorly. With a trump lead, you should be able to get a couple of rounds of trumps in, thus stopping declarer from getting club ruffs in dummy.
Are these choices always going to work? Mostly they will, but when they don’t, you should accept it. Of the points made in these four hands, the one about not leading aces is the big one. Just remember this helpful acr0nym, IYLAAYWOLWYSHL: If you lead an ace, you will often learn what you should have led. Write it on your convention card under opening leads. You will get a lot of odd looks, if nothing else.