Most everything's been touched on already, but I'd recommend being familiar with your individual pads. Different pads will do different things with pucks. Some will deaden pucks, some with harder materials will push them out more. Every goalie should know his pads.
I'd recommend when giving up bad rebounds to let your defense clear it if possible. Be like a wall and resist the urge to pounce on a puck as that can open you up for easy goals.
I'd say the best way to learn rebound control is just to get out there with a friend. You'll learn the fundamentals of it REALLY fast, but like the last poster said, it will be hard to master especially in a game situation. Start with your friend shooting pucks against the ice softly and learn how to deflect the puck with your stick, then same thing with pad, then keep having your friend kick it up a notch shooting harder and higher.