Play techniques (bridge)

Techniques by declarer

*establishing long suits
*finessing
*when not to finesse
*the holdup (mostly at NT contracts)
*timing
*unblocking
*blocking
*managing entries
*trumping
*the crossruff
*when to draw trumps (how many rounds to draw)
*when not to draw trumps
**ruffing losers
**discarding a quick loser
**complete crossruff

Advanced techniques by declarer

*card reading (counting the hand)
*the duck
*the dummy reversal
*the endplay
*various coups
*the squeeze
*the principle of restricted choice
*the theory of vacant spaces (probability)
*techniques for playing various suit combinations
*percentages
*the safety play

Techniques by defenders

Defense is commonly seen as much harder then playing as a declarer mainly because the defenders have less information than the declarers. It starts from an opening lead. The opening lead can often determine the number of tricks the defenders can win. It's so important that the common opening lead conventions are usually included in the convention card (bridge). Below are the most commonly used conventions:
*Which card to lead in a suit
**the higher card from a doubleton to show count, create ruff opportunity, and avoid blocking (with or without honors)
**the top card from a "three-card" sequence with honor(s) to cash and possibly establish the suit (strong enough to do so)
**the smallest one or the fourth-highest card in a suit with honor to encourage return and help establish the suite (both suit and notrump contracts)
**A or K from a suit led by AK for suit and notrump contracts (depending on conventions)
**one card from a three-card suit without honor in suit and notrump contracts (depending on conventions)
*Which suit to lead
**singleton/doubleton for ruff in the second/third round
**longest and strongest in notrump contracts
**partner's bid suit
**trump suit
*Aggressive or passive leads

After the opening lead, the most important technique is Signal (bridge). There are three types of signals: attitude signals, count signals, and suit preference signals. Among them, the attitude signals are most frequently used. As its name shows, signaling is to disclose one defender's card information to the other defender (and the declarer as well).

Since the defenders usually have access to less information, communication is more crucial in defense. As seen above, both opening lead and signals disclose valuable information to help communicate. Other techniques for better communication include unblocking (bridge), overtaking (bridge), ducking (bridge), etc.

Generally, it's more effective for a beginner to learn play as a declarer before play as a defender since techniques for defenders are related to the declarer techniques, which are easier to understand.