I've blogged about this in the past, that I don't really understand how to serve a table tennis ball despite so many ten of thousands I've served over the past seven years. It was the same when I was growing up playing tennis. I served many balls in practice and in matches but I didn't really understand on a basic visceral level what I was doing until one summer when I just got it. In tennis when I was growing up there were two main serves that people used: flat and kick. The flat serve was your first one, just hard and fast, out wide or up the T as we used to say. The kick serve was your second one, which in table tennis would be called a side topspin serve. This serve was slower and the topspin was there so that you could clear the net by a lot and still bring the ball down in the service court. Because of the side spin component it kicked a bit (to the server's right if she was right handed) hence the name.
I couldn't for the life of me get the ball to kick for many years until one summer my teenage brain just figured it out on its own. When I got that I understood serving on a deeper level: how to position my body, arm, and racket to get all sorts of spins, speeds, and placements on the ball. From then on I "knew how to serve" whereas before that on a basic level I didn't.
Fast forward 30 years and I'm going through the same thing in table tennis. I watch the advanced players serve and I know there's stuff going on that I don't get. But this time of course I know that I don't get it and I also know it's more or less pointless to ask or to try to get it. You just have to practice, practice, practice, and wait and be patient.
So a few weeks before going to London I was doing my usual serve practice at the table at work while taking a break and it just started. I knew immediately what had happened and wasn't too surprised, only that it had taken so long. But then again everything takes longer when you're older. Before this I had a lot of trouble keeping my serves short and in general had pretty poor control over the depth. Also the spin on my serves (I feel) was easy to read because of the large racket motions I used to create each type of spin. Now all that's different, I can serve short (2-3 bounces on the other side) medium (second bounce at end line) or long (one bounce) all with equal ease and the spin disguise is very much improved.
There's a chopper at one of the clubs I play at who I had never beaten until three weeks ago. Last week I won fairly easily and he commented after the match that he couldn't return any of my serves. I won many of the points outright on serve or with easy 3rd balls. (Of course we are talking about usatt 12-1300 level here, such are my credentials.)
So what's the secret? I'm going to tell you with the warning that it's not going to make any sense and you shouldn't pay any attention to it. The trick is not to hit the ball, but to "catch" it on your racket while at the same time snapping your wrist very hard. The wrist snap is the only important part of the whole motion and it happens in the last few inches before contact. Everything else you do with the racket before and after that is pretty much irrelevant (as far as spin and placement goes). When you get it right you can feel the topsheet grip the ball and fling it forward. All of your energy and concentration should go into timing the "catch" and the wrist snap to be simultaneous. All of the spin, speed, and placement variation come from very small changes to the racket angle and contact point (on the ball and on the racket face) during the wrist snap. And that's it. It's all about that little catching feeling and snapping your wrist so hard it feels like major tendons are liable to break. So now you know. Or not. Go and practice!