Stay calm

I learn this the first time I started playing in a league......Never get nervous. The easiest pret are the players that aren't calm. It is easy to steal the ball from a nervous player because it might be his first time playing. This is the main reason why rookies in the NBA are not clutch. The crowd and the thought that they are playing on the big stage is what get's them to make mistakes.

Follow through on your shot

Don't make the mistake to fade away on your shot. Lean in and the shot will have a better chance to go in.

Secret on how to improve your free throw shooting(shhh...dont tell anyone)

5 simple steps:
1)Get balanced
2)Look at the rim when you shoot
3)Bend your knees
4)Keep your arms and body center to the hoop
5)Always follow through

These were the steps that I was taught when I was younger and it has helped me ever since.

Force the dribbler to make the first move

Your the defender and the ball handler is just toying with your head, waiting for you to go for the steal while he dribbles back and forth and back and forth right in front of your face(I do this a lot). Your first reaction is to play in to his trick and go for that quick steal while he goes around you for an easy layup. Do not let this happen to you, while he continuously dribbles just move your eyes where ever the ball goes(or at least make it look like your awake), the ball handler will get bored and ultimately try to make a move. That is what you want him to do. If you make the first move he can anticipate it and go right around you. If he makes the first move, you can anticipate where he is going with the ball and the result will probably be a missed shot, a steal, or a block. All the good NBA defenders use this technique. In fact I was actually taught this method by a former NBA player!