http://www.serveunlocked.com

The key to developing really effective tennis serve technique is accelerating the racquet along the circular path. Most club and junior tennis players visualize the racquet path in a very linear way and do not achieve the maximum angular momentum of the racquet. Another idea to have in mind is the imagine accelerating the tip of the racquet rather than the face of the racquet. You should feel the pull of the racquet rather than pushing or hitting the ball.