You need to just understand where the ball is and how to use your body. Timing your jump the right way is crucial. Learn how to use your body to shield the receiver and box him out, again, much like a rebound. Trying to beat a receiver to a ball can be a lot like you're posting him up. Rebounding is great practice because you can employ those skills - body position, leverage, timing - a lot more than you might in a football game or practice if the quarterback doesn't look your way.