chiz, if you try doing a short serve and it is going long without even landing twice on the table, then your bat angle at impact is NOT totally horizontal to the table at impact. Could also be poor bat speed at impact with too much solid contact. A lot of us THINK we impact the ball on the bottom, but we don't. When we backswing, we naturally tilt the bat open. That is OK as long as you correct the angle by the time of impact.
If you are able to make a double bounce on the other side, but only with weak spin, then there could be several things going on.
1) Your bat speed at impact is too slow. Without enough bat speed at impact, you wont get much spin. You can make a very fast bat speed with a very short stroke. It is all about being loose and accelerating the bat with good timing control and feel.
2) Your swing plane may not be horizontal. Many players try to swing downwards some at impact, this takes away from the ball going forward, so players try to graze it even more and make a weak contact
3) You were DEATH gripping the bat. When a player is tight, he cannot accelerate the bat worth a crap.
If you get heavy underspin, but the ball still bounces 2-4 times and goes off the table, then there was just a tiny too much solid impact. Graze it a little more and be UNDER the ball a little more. It doesn't take much of a deviation from an effective bat angle to make the serve go longer than you want.
The looser you grip the bat, the easier time you will have.
When you practice, the IMPACT is the most important thing. The bat speed, the timing, the place on the ball where you impact (bottom or even a little to the front), how you accelerate the bat... these are a the MOST important at first. After you get the feel for this impact, there is only a tiny correction to control the height and depth with your bat angle and where you are trying to make the first bounce. You do not need to land it right next to the net, just a little past halfway is enough for a good short serve. Around 2/3 the way to the net and a little higher bounce than normal for a ghost serve.
In a real match, a ghost serve to a decent opponent is asking for that serve to get flip killed. It is simply too high.
yet, it IS important to learn how to do this serve because...
1) it looks really cool and makes you feel good
2) it helps you master the kind of impact you need for short serves, which are essential as your level improves.