The original opening is materially varied by the character of the final declaration, the system of leading against a No-trump being quite different from that employed when a suit is Trump.
HOW TO LEAD AGAINST A NO-TRUMP
When the partner has not shown strength, the leader, against a No-trump, should open his own long suit. If he have two long suits, he should pick the stronger except when he has declared it, and has not received support from his partner, in which case it is generally wise to try the other. The possible exception to the lead of a long suit against a No-trump is when that suit has been declared, has not been helped by the partner, and the No-trump has been subsequently bid to the right. In this situation, with a tenace in the long suit, it is sometimes advisable to try, by leading another suit, to get the partner in, so that he may lead through the Declarer's strength in the suit called by the leader. This, however, is a dangerous expedient when the partner has not declared. Should a suit be guessed which the partner cannot win, one of his high cards is apt to be sacrificed, and not only nothing gained, but the advantage of the lead transferred to the adversary. If two high cards be missing from the tenace suit, as in the case when it is headed by Ace, Queen, Ten, or King, Knave, Ten, and the Declarer hold the missing honors and one small card, it will take two leads to establish the suit. It is not likely that a partner without sufficient strength to declare will be able to get in twice, and trying to put him in once is most apt to establish a suit for the Declarer. Therefore, as a general proposition, unless the partner have declared, the tenace suit should be led. When, however, the partner has shown a suit, opening it, in preference to a tenace, is elementary and compulsory.
When the partner has declared, the leader should open the suit named unless satisfied that his own affords a more potent weapon for the attack.
There are only three conditions which justify the leader in assuming this, viz.:—
(a) When the leader has called his suit and his partner has advanced the declaration.
(b) When the leader's suit is headed by Ace, King, Queen, or King, Queen, Knave.
(c) When the leader has only a singleton of his partner's suit and has several reëntries.
Innumerable tricks, games, and rubbers have been thrown away by a leader who, considering solely his own hand, has started with his suit in preference to that of his partner. There is some peculiar characteristic in the composition of many players which magnifies the value of their own cards, so that they seem of greater importance and more desirable to establish than their partners'. Even experienced players have been known to commit such an Auction absurdity as opening a suit headed by a Knave, in preference to the suit named by the partner, which, of necessity, contains the strength requisite for a Trump declaration.
It is fair to estimate that ten tricks are lost by denying the partner's declaration to one that escapes the player who leads his partner's suit in preference to his own.