Every good volleyball player should have an overhead float serve in his or her arsenal. For an overhead float serve to be most effective, the ball should not spin. A ball that does not spin is unpredictable in its trajectory and speed making it hard to read where it will land. Also, because the ball is not spinning, it tends to rise, weave and dip, further confusing the recipient, much like the effect of a knuckleball pitch in baseball.
For the right handed server, the proper stance for an overhead serve is to start with most of your weight on your back (right) leg. Your left foot should be forward for balance (like you are taking a step towards the end line). Your body should be facing the direction that you are serving. The tossing arm (left) should be held out perpendicular to the body, with the palm of the hand up cradling the ball. The hitting arm should start with the elbow back and the forearm and hand pointing through the ball and towards your target.
It starts with the toss
The toss is paramount to an effective serve. The toss should lift the ball straight up to a height of 12 to 18 inches above the tossing hand from the point the ball is released. The ball should be released at about eye level. In order for the ball not to have any spin during the serve, the ball should be tossed without any spin.
Finishing the serve
Once the ball is tossed, the serve action should be one fluid motion. The players weight should be transferred from the back leg to the front with the front knee bending slightly. The back leg should also transfer up on to the toe for balance and stability while hitting. Contact with the ball should be made at the highest point of the toss. The motion of the hitting arm should start with the arm being brought back and the hand being raised.
The forward motion of the arm is started with the shoulder and elbow leading the hand. The hand then accelerates through the ball with an almost punching motion. Contact with the ball should be made with the heel of the hand and at the center of the ball. The hand and arm should follow through pointing at the target.
Putting it all together
A properly executed overhead float serve will be hit hard, have a relatively flat trajectory and an unpredictable course. All of these effects will make it hard for the receiver to judge and pass effectively.