Serve Harder Training Program: Serve 10 to 20 mph faster in 90 days! By Joseph Correa Learn how to drastically change your serve through 6 exercises that will increase your racquet head speed and acceleration in a very significant way. This book includes: 6 Tennis Serve exercises 3 charts that will teach you how to do them in an organized manner. Detailed explanation on each phase of the charts. 6 Serving tips 15 Serve drills