I blabbered about how you can serve in at least nine ways: 3 (flat, kick, slice) x 3 (to the middle T, to the body, out wide), which parts of the ball the racquet face should be in contact with when making different serves.
I said it is more effective to mix it up and keep your opponent guessing than to try to hit with raw power.
I said that the serves of some professionals are so well disguised that when they make different serves, the toss and the service motion are the same. That makes it very difficult for the opponents to make the serve.
Not that I can serve like that of course, but I believe this is something important to know. I've heard it said that success in a profession rests on one's ability to make finer and finer distinctions between differences, and I think this can be applied in all sorts of domains.
So maybe there's much more to know about tennis serving than just these 3 x 3 ways?