The key to hitting wedge shots is to pivot your shoulders, rather than manipulate the club with your arms and hands. Regardless of the length of the shot, make the same size pivot on the backswing, turning until the left arm is just above parallel to the ground and forms an L with the club shaft (picture 3). To vary a shot's distance, alter the pace of the pivot on the downswing, not the length of the backswing. Here's my favorite pivot drill.
1. Lay the club you're going to work with—any one will do—on the ground with the toe touching a golf bag. Put a mark on the ground at the butt end of the club. Now pick up the club and address the ball so that your back foot touches the mark (picture 1; I have left another club in place as a visual aid).
2. Take a normal swing. If you pivot properly, the club won't touch the bag (picture 2).