First of all, hold on tight to the ball, but not too tight. Make sure to put your hand on the ball in a way so that the the pointer finger is as close to the point of the ball as it can be. Wrap the thumb around the ball and place the rest of the fingers in-between each lace. Your natural grip is the best way to hold the ball.
Secondly, standing correctly can impact the way you throw. In order to throw accurately, you will need to know how to stand. Spread your feet just slightly more than shoulder length, and place the opposite foot from your throwing arm forward. The majority of your weight should be on the back leg, and only part of your weight should be in front. When you throw your weight should transition onto the front leg.
Lastly, you need to release at the right time. Before you release it you will need to arch your shoulders back. Dropping your hand that is not throwing beneath your chest, you will throw the ball forward over your head. Remember to allow the ball to roll off the fingers beginning with the pinkie and ending with the index finger.