The following hands are a good example of when not to finesse; in other words, if contract is sure without making a finesse, avoid the risk.
N. 46 108 ✓ JlOxx • KQxxx ▪ x x W.
• K x 11, Ace • J 10 x x x • J 10 x x x S.
4. AceQJ 9 xxx
K Q • x x • Acc Q The contract was Four Spades by S and W led out his Ace of Hearts and then the J of Clubs; S is now in with his Q of Clubs and can afford to lose two more tricks; the Ace of Diamonds and the King of Spades. He led a small Diamond to establish an entry in the hand of dummy; E took the trick with his cold Ace and E and W set up a cross ruff in Hearts and Diamonds.
S should have led the Ace of trumps at once and then the Q to clear the suit and nothing can defeat him then if the trumps break 2-2. Of course it was very bad luck finding his opponents with two cold Aces but to embark on a finesse is unnecessary; if a Contract lies, do not bother about overtricks if there is a risk entailed but go the simplest way to your goal.
The key to the whole thing is a simple calculation of odds; if the finesse comes off in trumps, then it is true there is an addtional 30 points above the line, but if it fails there is a possible loss of hundreds of points. What point is there in taking such odds as these? The same argument applies to doubling and redoubling. Count the odds; if your double comes off—a risky double, in which you can scarcely expect to set the contract by more than one trick—is it worth making? Or is a redouble worth it if it opens the bidding again and may give the opponents a chance to call? It is the rapid review of factors such as these that mark the steady player, who in the end must win.