The ABC’s of good dummy play: learning to handle individual suit combinations correctly. For example, with Q-10 opposite A-K-4-3-2, declarer’s percentage play for five tricks is a finesse with the ten.
At today’s 3NT, declarer starts with eight top tricks. The clubs will break 3-3 only a little more than a third of the time — no doubt less than that when West has led a club — so declarer would like a second diamond trick. If he wins the first club in dummy and leads a diamond to his queen, he goes down. West takes the king, and East still has a double stopper in the suit.
But declarer should be in no hurry to finesse. At Trick Two he can play a low diamond from both hands.
South wins the next trick and cashes the ace of diamonds. The king happens to fall, so he is safe. If instead both defenders played low, South would lead a heart to dummy to return a third diamond toward his queen. He would get two diamond tricks whenever the lie of the cards permitted.