Do not play your adversary's game for him, lend him no aid in establishing his suit.
Take all your finesses against the player who holds an established suit.
If, as dealer, you wish to make four tricks in a suit with but three in sight, give the adversaries a chance to discard.
When there are tricks that the adversaries must win, try to make this necessity a benefit to your hand.
Rid yourself of any high card which may interrupt the continuation of your partner's suit.