You have a smooth service motion, a good toss, and decent accuracy, but you can’t generate enough power. Sound familiar? Your problem may be that you don’t shift your weight forward. Adding a step to your serve might help. To master the technique, which is called the “pinpoint” stance, put thin rubber targets, or poly spots (available at tennistrainer.com), at the baseline where you normally put your feet to serve. Stand on the targets to serve and after you toss the ball, move your back foot onto the target next to your front foot. The forward movement will shift more of your weight into the stroke.