Tennis players go for aces the way bowlers roll for strikes. The trouble is they miss more often than they score. The serve is a high-pressure shot - precisely because the server knows he is solely in control of the play. This is why smashing aces makes you feel invincible, and double faults are more demoralizing than a rush-hour breakdown.
The key to a good serve is the throwing motion. Imagine you're Sonny Jurgensen hurling your racket into the opposing service box (if you have a very old racket, try it). Beginners who fail to get the racket all they way back into a "back scratching" position end up pushing or straight-arming the ball into the net.
A classic serving motion like Bjorn Borg's is one smooth and continous action without pauses or "hitches." The racket arm rotates like a windmill on the back-swing before it reaches up to strike the ball.
A nice service motion without a well-placed toss is usually a wasted effort. Players who toss up to nose level or beyond Wilt Chamberlain's reach serve more double than they care to admit. A good toss should travel no higher than the racket and arm extended. Release or loft the ball as though you were guiding a bird into flight - don't jerk it up like an underhand shot-putt.
Every good serve has rhythm - coordinate your arm movements like a ballet dancer. The racket arm and the tossing arm should move down and up in unison. Use plenty of wrist snap at contact to add Roscoe Tanner-like zip to your left side and move in behind the ball like a hunter after his quarry.
Develop a reliable serve that can be consistently directed to your opponent's weaker return, usually the backhand. Don't revert to poking at the ball on the second delivery - unless you want the return rammed down your throat. Take the same full swing but add some slice or twist for greater control and net clearance.
Q - Where is the toss supposed to go for a flat serve as opposed to a slice serve?
A - for the flat serve, toss the ball slightly to the right of center and in front of you. For the slice delivery, toss it farther to your right and sweep across the outside of the ball.
Q - I know I toss the ball too high, but if I lower my toss I can't complete my swing in time. What should I do?
A - You are probably pausing at some point in the course of your swing. Try to swing with one fluid, uninterrupted motion, the way Roscoe Tanner does.
Q - Is a slice serve better than a flat one?
A - A slice serve is easier to control, but a good flat one will produce more aces, provided you can get it in.
Q - I have trouble controlling my toss. Is there any way to improve my technique?
A - You can practice your toss in front of a mirror. Make sure you don't roll the ball off your fingertips and that the ball consistently lands in a small semi-circle in front of you.
Q - My American twist serve doesn't seem to have much kick. What could be the problem?
A - You are probably not tossing far enough to your left and behind you. For an exaggerated kicker snap your wrist from left to right and finish with your racket on the right side.
Q - Does it matter what kind of grip I use for my serve?
A - Beginners find the forehand grip most comfortable, but as you progress you'll find that a backhand or Continental grip will enable you to hit with more snap and spin.