Loose Wrist on the Serve
A loose wrist is essential to not only gaining more power, but control, spin, placement, trajectory, everything. To get a looser wrist you also have to remember to loosen the grip and the fingers. Just like trying to throw a ball if you squeeze tightly it does not go anywhere. You have to loosen to allow the wrist to accelerate. Many of the top pros current and past will even take one or two fingers off the bottom of the grip to insure that they are keeping their grip, hand and fingers loose. Try it with a very loose had and just allow the wrist to snap naturally. There will be some pronation, but you don't want to force the pronation as you might hurt your wrist and/or elbow in the process.