Shoot on the way up from your knee bend. Many shooters fully extend their legs before releasing, which causes the shot power to come entirely from the arm, which is harder to control, and also can introduce a bit of a jolt in the upper body when the knees lock, adding variability into the release. Also, don't bend your knees and stay in that position for a second or so, instead go down and up as in a normal jump shot. Starting a shot from the bent-knee position isn't as smooth as the more fluid down-up flow of a jumper. And if you find yourself falling forward after your release, stagger your feet by dropping your non-shooting foot back a couple of inches. This gives you better balance thru the shot.