Instructions
Swing the controller forward from low to high. Rotate your wrist forward so that the Wii controller buttons face down when you make contact with the ball; this will give the ball topspin.
Swing the controller forward from high to low. Rotate your wrist backwards, making the Wii controller buttons face up, when you make contact with the ball to perform a backspin.
Swing the Wii controller from right to left to put a sidespin on the ball when it is hit to your forehand; swing from left to right to put a sidespin on the ball when it's hit to your backhand.