Stand sideways to your opponent, with the dodgeball held in your rear hand.
Raise your front foot and lunge forward, as a baseball pitcher would.
Extend your rear hand, which is clutching the dodgeball, behind you as you begin your lunge forward. As your foot lands, your arm should come over the top of your body, so that both your forward momentum and your arm motion are pushing the ball forward.
Release the ball as you land. You should release soon after the ball passes over your body and your arm starts to pull the ball down.
Bring your rear foot forward as you land on your forward foot and release the ball. You should end up with your hips squared to your target.
Follow through with your throwing hand, which will help you to throw more accurately and hit your target.
Look out for balls being thrown at you as you release the ball. An opponent concentrating on throwing makes an ideal target.