hands together and your shoulders up. your hands should form a rough semicircle as you bring your racket hand back and your ball hand forward.
at this point your hands are coming up to shoulder level. now there are two steps that happen in conjunction. your racket arm should bend and bring the racket behind your back, ready to swing. at the same time you will toss the ball with your other hand. your toss should be high enough that you can make full extension as you swing. it should also be just in front of you. you should not need to reach for a toss that is too far forward 