I advocate a similar progression as NL does for learning short serve touch.
I believe it is real important to do it all in progressive stages without any effort or expectations towards making a successful short serve right away.
One needs the timing and relaxed muscles to go along with the bio-mechanics. it doesn't happen overnight. it took me 6 months practicing every day to get my short serves to land double bounce more than 1/2 the time.
Stage one, learn the bio-mechanics, impact point on BOTTOM of ball, the basic sequence and timing. Practice it by standing up away from table in a hall or rest area, serving to a spot a meter or two away and get ball to spin back. Do that every day as much as you can, minimum 5 minutes a day for a month or more. The goal is to learn the basics and get some reps without pressure, and develop a consistent impact under the ball.
Stage two, do the same thing, but stand a meter or more behind table, impact ball, make it go out, bounce high on your end of table, go over, and start spinning back. This drill reinforces the mechanics and touch, and like the other one, gives you a means to practice without pressure of having to succeed right away, plus you still get to see progress.
Stage three, take it to the table. Serve deliberately high bounce first bounce a foot or so from the net, let it go over net, and have it spin back towards you. This practices the touch more, practices landing it on a target area, and still can show you your progress. this isn't a match serve, but practices all the important mechanics, touch, and landing zone you need.
Stage 4, now you are ready to take it to the table, work on impacting ball just under chest height and make first bounce just past halfway to net. Let ball bounce high, it is OK, you are trying to fine tune your basic impact point height (near chest, and later a tad lower for a lower ball) and you are developing relaxed touch in a more real scenario. Dont go for the tight low serve just yet, simply get used to landing it with good spin and controlled first bounce zone.
Stage 5, now you are ready to try making the bounce lower. Try for impacting it somewhere between belly button and chest, preferable somewhere in the middle of that zone or a tad higher. Control first bounce, learn where you have to aim to get the ball to bounce low, whether that is a tad in front of half or right at half or a tad behind it, learn variation and above all, use a very relaxed grip.
Once you do that enough, you develop the touch and have learned how changing impact height and landing zone and how pressure affects the ball.
This gives you the foundation for a short serve. now you are ready to start adding side spin, and later, deceptive arm/wrist after motions.
Later, you learn how to impact different parts of the ball in different ways to produce a totally different ball with the same serve motion. That is a big-time requirement for a player to develop nasty deceptive serves with variation at will.
later, these serves go along with your serve/attack plan, and/or work to prevent other better players from attacking your serve or at a minimum control their options.
Serve is both science and art... both ends need practice... REGULAR structured practice with an objective and long term goal(s).
