On the hand below, South was in a 6S contract and had to find the best line to avoid two losers. Plan your play after West leads the Queen of hearts.
NORTH
♠ KJT9
♥ 762
♦ AQ
♣ 6543
WEST EAST
♠ 43 ♠ 52
♥ QJT ♥ 93
♦ T7543 ♦ KJ986
♣ KJT ♣ 9872
SOUTH
♠ AQ876
♥ AK854
♦ 2
♣ AQ
There is a sure loser in hearts and declarer also has a potential club loser. Of course if the King of clubs is in the East hand, the club finesse will succeed and the contract can be made. An alternative possibility is to finesse to dummy's diamonds, trying the DQ; if that succeeds, South's CQ could be discarded on the second diamond from dummy.
Lacking any clues from the bidding, it is a guess which of those two finesses to opt for and either would provide a success rate of only 50% (and both fail as the cards lie). How can you improve your chances?
What if you could make an opponent lead into the jaws of one of your A-Q suits? Here is how you would go about trying to achieve that end.
First draw trumps. Next, cash the DA and ruff the DQ. Then, cash the remaining heart honour, and now, play the third round of hearts which will lose. If East wins (having started with three hearts), a club from that hand will leave you having to resort to the club finesse after all. But so long as it was West who started with three hearts, the contract must succeed; West will now be stuck on lead and the position will look something like this:
NORTH
♠ T9
♥ -
♦ -
♣ 6543
WEST EAST
♠ - ♠ -
♥ - ♥ -
♦ T75 ♦ J98
♣ KJT ♣ 987
SOUTH
♠ A8
♥ 85
♦ -
♣ AQ
If West leads a diamond, declarer will ruff in dummy and discard the CQ from hand, then claim (remember, the hearts in the South hand are winners as there are no others outstanding). West does better to lead a club, hoping partner has the Queen (or better still, the Ace) but as declarer has both honours, that gives the game away too.
Many a hardened bridge player will tell you that "a peek is worth two finesses", but sometimes by making an opponent lead a suit you avoid the need for any finessing - or, for that matter, any peeking.