This deal is from the quarterfinals of the 2013 United States Bridge Championships. South held:

 

3
KQ942
Q10985
74
His partner opened 1 and he responded 1.

North rebid 2. This jump shift is natural and forcing to game. South bid 2NT, raised to 3NT. Everyone passed and the 3 was led:

 

AK108 AJ A7 KJ1092

3 KQ942 Q10985 74

Declarer doesn't have too many top tricks. Even if you were to count 4 top heart tricks, the communication is not there to cash them (unless the 10 falls or the suit splits 3-3). So, which suit will you work on to develop tricks, and how? If you play the A and another diamond, East follows low. Do you play the queen or the 10?

 

 

It's a good question, but a trick question. Yes, it is a good idea to know this suit combination. If diamonds are 3-3, it would just be a pure guess as to whether you play the 10 or queen on the 2nd round. What if they are 4-2? If the two is the two low ones you've seen from RHO, nothing matters. What if LHO has a doubleton? If they are two low ones, it won't matter much, but if he has a doubleton honor, the queen is the correct play. Why? Because if LHO has doubleton jack, you can pick up four diamond tricks by playing the queen. If he has doubleton king, you can never take 4 diamond tricks. So, you might as well take the 50-50 guess in a way that benefits you most when you are right. Summary of the diamond suit: Ace and low to the queen is the correct play.

Now, let's think about the deal as whole. If you misguess diamonds, then what? The defense will likely switch to spades and you have big troubles. You'll have to win in dummy and unless hearts come in (3-3 or doubleton 10), you are likely down.

 

Rather than rely on hearts or diamonds, you have almost a sure line for your contract. Play on clubs. Yes--win the A and at trick two, lead the K from dummy. Why the king? This is almost the same thinking as the diamond suit--if there is a singleton honor (unlikely, of course), you might as well play the card that has the most upside (a singleton queen will benefit you more than a singleton ace). The point, however, was to play any club honor. As long as there is no disastrous club layout, your plan will be to later play another high club honor from dummy. You are willing to lose to the A now and the Q later. This will develop 3 club tricks in the dummy. Those go with 3 hearts (you can overtake) and A-K-A in spades/diamonds.

 

This was the Real Deal:

 

 

Vul: None Dlr: North	AK108 AJ A7 KJ1092
Q964 10873 62 A65		J752 65 KJ43 Q83
	3 KQ942 Q10985 74

It turns out, the diamond suit was very friendly. Erroneously playing diamonds first might have worked. East could win the K on the second round and switch to spades. You'd still have to guess well to make the contract.

 

Playing on clubs at trick two is much better. Now, you don't have to guess anything. You have 9 tricks by brute force (3 clubs, 3 hearts via the overtake and ace-king-ace in spades and diamonds).