Here are the steps to the topspin serve:
1. Stand sideways to the baseline. Let both racquet and ball-tossing arm move down a little together before they part to start the take-up. With your weight moving forwards over your bent front knee, swing the racquet down past your body and and turn your hitting shoulder well away as you release the ball (toss the ball a little higher above your front shoulder).
2. As you lean in, bend the racquet arm elbow bringing the racquet up.
3. Drop the racquet into the throwing position as the ball begins to fall. Keep the tossing arm up as long as you can, using it to track the ball.
4. Straighten your legs and at the same time your racquet arm, elbow, and wrist, throwing the racquet head up almost edge-on so that the strings bite the ball, brushing up and across it.
5. Snap the wrist forwards so that the racquet face strikes the ball a glancing blow from below.
6. Completing its up and across action, the racquet leaves the ball and arcs up and out to the right as the rear foot begins to swing across the baseline.
7. Follow through with racquet down past the right side. Your back foot will come down inside the court but not so far over the baseline as for the first service.