Excerpts — Nick Bollettieri's Tennis Handbook-2nd Edition
For many years only one technique was taught for the serve. Set your feet shoulder-width apart, point your front foot toward the target, put your racket hand and ball-tossing hand in front of you at waist height, start with your racket hand and ball-tossing hand going down together and up together, and do not move your back foot until you make contact with the ball and step into the court.
Following are illustrations of several drills of each type discussed previously.
Let’s start with the facts. The energy created in a tennis ball that meets a racket breaks down into the following components: 60 percent of the energy comes from the string bed (the strings in the racket). 30 percent of the energy comes from the ball (a rubber object in motion with its own energy). 10 percent of the energy comes from you and your racket frame (frame only, not the strings).