Leading Through Dummy. The eldest hand, when he does not deem it advisable to go on with his own suit, may be guided in his choice by the strength or weakness of certain suits in Dummy’s hand. The play against Dummy is especially important at no trumps.
Suits which it is good policy to lead through are A x x x, K x x x, or any broken sequences of high cards.
Suits in which Dummy is long, or holds any of the regular high-card combinations, should be avoided; winning or high sequences being especially dangerous. To lead such suits through Dummy’s strength is an invitation to partner to force you in the suit led.
It is not necessary for you to be strong in a suit which you lead through Dummy; and if you are both weak, is often advantageous; especially if it avoids leading one of his strong suits.
With A Q 10 x; Dummy having J x x x; play the 10. If partner has the King you make every trick in the suit.
With A Q 10 x; Dummy having K x x; play the Q. If Dummy passes, you make two tricks; if he covers, you have tenace over the Jack.
With A 10 9 x; Dummy having J x x x; play the 10. If partner has the K, your A 9 is tenace over the Q.
With A J 10 x; Dummy having Q x x x; if the suit must be led, play the Jack; but such positions should be avoided, except in the end game, or when you play for every trick.
With A J 10 x; Dummy having no honour in the suit; if you must lead the suit, play the 10.