). When you are attempting a set, you should be attempting to center the ball in this triangle and using only the pads of your fingers to push the ball back up.
Try shrugging your shoulders while bending your arms at a slant during your sets and bumps. If you're moving from your elbows, chances are that you aren't going to get maximum power. When you set, it also helps if you form your hands into a diamond and look through as you're hitting the ball.