Surely a player of your bridge skills is familiar with most or all of the following tips you are about to read. But is your partner?
When defending a suit contract, there are two main techniques declarer uses to garner extra tricks:
(1) setting up a long suit in dummy, (2) ruffing losers in the short hand (usually the dummy.) If dummy comes down with a long and a short suit and you have the long suit bottled up, lead trumps because the long suit is not usable. If it appears that the long suit is usable, play an attacking defense going for outside tricks quickly. If the dummy comes down balanced, declarer has no place to get rid of losers and will eventually lose them, therefore you and partner should adopt a passive defense. Avoid breaking new suits if possible. Let them have what they have coming. Sit back and wait for your tricks. Your day will come.