Snap the wrist.
With so much force and spin being placed on the ball, maintaining control can be tricky. The ball will be finessed if you swing the racquet on edge. But to get on top of the ball and drive it down into the service box, Williams says, you must snap your wrist hard. "Eventually, [the ball] straightens out, you don't stay on edge all the time because you snap through with your wrist," she says, adding that you’ll know you've snapped hard enough when you follow through with your racquet across your front hip.