There is often considerable guesswork during the play, and if you are by nature a good guesser, you will do well in the long run.

All the same, a good cardplayer tries to avoid subjecting himself to a guess if he can.  He might guess as well as the next fellow when he has to, but his chief stock-in-trade is a talent for dodging guesses and solving his problems by other - and more reliable - means.

Assume you're West, defending against five hearts.  You could lead a spade, of course, because partner raised spades, but your best chance of defeating the contract lies in leading a diamond.  Your hope is that partner has an ace, in which case you're apt to beat the contract when you get in with the ace of trump, put partner on lead with his ace and get a diamond ruff for a one-trick set.

Declarer wins the diamond with the ace and leads a low heart to the queen at trick two.  It would be easy to go wrong at this point.  If you take the ace and lead a spade to partner's assumed ace, you wind up behind the eight ball.  Declarer wins, draws trump and concedes a club to the ace to make the contract. 

You could plead that East was more likely to have the spade ace than the club ace, but that would not be a good excuse for failing to guess which one he actually had.

Instead of consigning the guess to pure chance, it is far better to duck the first trump lead and take the second.  This gives your partner a chance to signal with a high spade or a high club, depending on his hand, and in that way all the guesswork is eliminated.

Source: Steve Becker, Globe and Mail, September 14, 2023