Serve
One of the most critical components of hitting a faster serve is the ability to hit "up" on the ball with a loose flexible whipping wrist action. And for players learning the serve for the first time, the concept of "hitting up" on the ball can be better understood by actually trying to do this action rather through an overdose of explanations. The weighted racket should make the feeling of hitting "up" on the ball MORE obvious.

Exercise:
While keeping the wrist loose, for players of all levels, start with your elbow up and your racket head pointing towards the ground and repeat the action of hitting "up" on the ball at least 10 -20 times while following through and you will not only grasp the concept of "hitting up" faster, but you will strengthen the muscle and tendons associated with this action. Once you have mastered this action, shadow-swing the whole action of your serve as well. Daily practicing of this action combined with all the other components will result in a faster, harder serve and hopefully, if you are accurate enough, more aces!!!