1) Get in the Offensive Player's "Bubble"
The bubble is the private area of an offensive player. You know you're in a player's bubble when you can make his shot, pass or dribble difficult.
However, you don't want to be too close to your man. Basically, you shouldn't be so close that the offensive player can beat you with one step. But at the same time, you have to be close enough that you if you stretched your arms forward, you can knock the ball away.
Bother him...irritate him...make him worry!
2) Get Low: A good rule to follow is to make sure your head is lower than the head of the player you're guarding. Staying low allows you to move much, much quicker.
3) Dictate Where the Ball Goes
The offensive player can either shoot, pass or dribble. You want to make shooting and passing difficult for him/her by being in their "bubble"...
If they dribble the ball, it'll be to the left or to the right. By overplaying him on one side, you can force him to go only one direction.
The advantage of playing defense in this way is that you know what the offensive player is going to do next...you'll be prepared. By making passing or shooting difficult for him, and by forcing him either right or left, you know the direction the player is going.
Remember, take away the player's options and dictate where the ball goes.
4) Position You Hands
If the offensive player is in shooting range, you should have one hand ALWAYS up, ready to block the shot. Even if you can't block the shot, you'll be able to get your hand in the player's face and distract him.
The other hand should be out and low, ready to poke at the ball if the player dribbles or passes.
So one hand up, one hand low...both hands out towards the player, ready to bother and distract during a shot, pass or dribble.
5) If You Get Beat Off the Dribble
If the offensive player gets by you, react QUICKLY!
Immediately turn around and get super low, staying right behind your man, and trying to run faster than him.
By getting super low, you'll be in position to poke the ball away from behind. This is an easy way to get steals.
Always, always, always follow your man immediately after you get beat. Be on his back and ride it. He should feel you breathing on the back of his neck.
The key is to react very quickly after you get beat, and to stay super low. Think fast!
The above defensive tips need practice, just like any other skill...
Don't treat defense as a secondary priority. Coaches love defense, and it can get you a starting role on a team or even a scholarship.
Be known as a defender. Work at it, practice the skills, and try to improve daily.