How to Jump Serve a Volleyball
To jump serve a volleyball, start by standing 2-3 feet behind the back line since you'll want to throw the ball high and step to the line to gain momentum for your jump. Next, look at how the opposing players are positioned so you can aim your body and serve toward the empty spaces. Then, toss the ball up and in front of you, and jump up as you hit the ball with your dominant hand. Make sure you hit the center of the ball as hard as possible with the heel of your hand to ensure that it clears the net.
Position yourself. Stand two-three feet behind the back line. You will want to throw the ball high and step to the line in order to gain momentum for your jump. Start with your left foot forward if you are right handed, and your right foot forward if you are left handed. You will take a three step approach. Aim your serve. Look to the positions of the players on the opposing team and try to aim your serve in the empty spaces. You want to hit the ball into “dead zones”.  This means that when you hit the ball, you want it to land between players, so that they have to communicate about who will hit the ball back. Position your body so that you are facing one of the dead zones. Turn your hips and shoulders toward the area. You should not have to turn your head to look at it. Toss the ball in the air. To do a float serve, use both hands. To make the ball spin, throw it up with your dominant hand with a topspin. Toss the ball high and in front of you. You should be able to do a approach before you hit the ball, so make sure that you throw it in front of you and high enough, so that it floats just behind the serving line. A good rule is to throw the ball the way that you like the ball to be set to you. If you like your sets low, then throw the ball lower. If you like your sets higher, throw the ball higher. Jump to hit the ball in mid-air. Do your regular hitting approach: Slow left step, and then two fast steps: right, left. Do the opposite if you are left handed. Jump with both feet, and hit the ball hard with your dominant hand. Aim your jump so that you remain in the serving area. If you hit the ball when you are outside the service area, the serve will be void. Hit the ball midair. Contact it with as much surface area of your hand as possible, and flick your wrist for a topspin. Hit more with the palm of your hand for a float serve. Hit it as hard as possible. This is where the force and momentum of the jump serve comes from. Contact the ball with a fully extended arm and jump high. If you do, the ball should clear the net and land deep. Aim the ball and follow through. When hitting the ball, your eyes should be on the ball. After you've hit it, bring your hitting arm down. Point your hand toward the place that you want the ball to land. Follow through with your eyes as well. This will ensure that you focus on the ball from the moment of contact until your follow through. Land your jump. As long as you were behind the service line when you hit the ball, your serve should be legal. However, to be safe, you should try to land behind the service line as well. If you overshoot your landing, you may accidentally hit the ball too close to the court. Land with both feet. Keep your knees bent to avoid any injuries. Prepare eight balls for the drill. Place a pair of balls at four intervals along the court. The first pair should be at the net. The next pair should be three steps back, and the next pair three steps back from that. The final pair should be at the serving line. Placing balls close to the net gives you a good idea of the height you need to extended your jump and your arm in order to get the ball over the net. Hit one ball from each pair over the net. Do not jump to hit the ball. Instead, toss the ball high in the air and swing your arm up to hit it. You should hit the ball when your arm is fully extended. Start with the ball closest to the net and move backwards until you are hitting the ball from the serving line. It is important that you do not jump, so that you get a sense of how long your body and arm should be extended. You want to use the same position when you jump serve, with your arm fully extended. Hit the second ball from each pair over the net. This time, jump when you hit the ball. The first hit, close to the net, should give you an idea of how high you should jump. Each time you hit a ball further away, you should be hitting it a little bit harder. As you get back to the serving line, use everything that you have learned thus far. You should be jumping and fully extending your arm just as you did before you were jumping. You should also be jumping as high as you had to when you were serving close to the net. 
Position yourself. Aim your serve. Toss the ball in the air. Jump to hit the ball in mid-air. Hit the ball midair. Aim the ball and follow through. Land your jump. Prepare eight balls for the drill. Hit one ball from each pair over the net. Hit the second ball from each pair over the net. 