You must insure that you are playing defense in the right position so that you can defend to your greatest potential. First you must bend your knees so that they are half-way bent (half way from being totally straight and totally bent) so it almost appears that you are sitting in mid air. You also must have your butt 2 inches behind your heels. Then you spread your legs so that your feet are slightly more than shoulder width apart. Rotate your left foot out and place your right foot foreward. Keep your left hand down to stop the dribble and your right hand up to block his line of site for passes and shots. Do not keep your fingers straight, you are asking for a jammed finger. instead bend them in a little, you will catch/block the ball a lot better.