Don’t play the first good move you see. Look around for an even better one.
The two most common (and often fatal) mistakes in chess are moving too fast and overlooking opponent’s threats. Sit on your hands until ready to move.
If your opponent is in time trouble, don’t rush your moves. Take some time to find surprising moves that force your opponent to think.
Don’t be afraid of higher rated opponents. They have more to lose than you do. Have some fun and learn.
Take no prisoners. Draw only if you must. If offered a draw, make sure you understand what it will mean if you accept it. In general, don’t accept a draw unless you’re losing.
If you touch a piece and your opponent calls you on it, put the piece back on the board and search for the best move for it. Don’t hold the piece in your hand while thinking.
Be aggressive, but play soundly. Don’t take unnecessary chances.
Make sure EVERY move has a purpose.
If you know your opponent’s style, take advantage of it. But in the final analysis, play the board, not the person.
Don’t check needlessly. Check only when it accomplishes something useful.
Answer all threats, but do so while trying to improve your position and/or posing a counter-threat.
Never play a risky move, hoping the opponent won’t see it.
The goal in chess is to play the best move in every position.
Winning at chess basically consists of creating and exploiting opponent’s weaknesses.
Play slowly. Haste and carelessness are greater enemies than your opponent. Accuracy, not speed, is essential in chess. Be patient. The reward for speed is a legacy of lost games.
Be serious while playing. Don’t talk to your opponent during the game. If he or she talks to you, complain to the leaders. You can socialize after the game, not during it.