Drive with your knees.
As with a baseball pitch, a tennis serve's power comes from the thighs. “As the ball is releasing, you're bending those knees, because a great serve comes with a great knee bend. You've got to work those legs," Williams, adding that this is even more important for shorter players without long arms and the ability to stretch. After bending your knees, you want to jut your front hip toward the court to start shifting your weight forward. “If you've ever seen a tennis trophy, the person has that perfect," Williams says. "At this point you've got your toss-up, you've got your knee bend, and the left hip is forward so you're ready to pounce. You're like a spring. You're going to spring straight up.” As for the finishing point, you always want your front foot to land inside the court, in front of the baseline. Otherwise you are not driving off of your legs enough. "It'll make a massive difference if you land inside [rather] than outside," says Williams.