Instructions
Press the "A" button on the Wii remote to toss the ball up and begin your serve.
Swing the remote when the ball is at the top of the lob and your serve will be much faster than normal. If you are only slightly off on this timing, the serve will be average speed.
Put topspin on the ball when returning shots to make the ball move faster once it hits your opponent's side of the court. Twist the remote down as you swing. This works for both forehand and backhand shots.