I'd imagine making sure that you have solid technique would also be a big one. If you have wonky technique that's putting a lot of strain on your arm because you're not using your whole body, you'll get hurt a lot more often.
I'd imagine bad groundstrokes are going to hurt your arm. Bad footwork might hurt your hips or knees (for example, if you always use closed stance and twist around your planted foot). And a bad service motion or ball toss might put a lot of strain on the back.
Also, if you can try and keep relaxed when you hit it should take away some of the harshness of the impact from the ball, since your arm won't be absorbing all of the shock.
Also, perhaps changing your style of play would help. If you're a grinder, it's going to be tougher on your body.
Last edited by TheCheese; 10-05-2012 at 02:27 PM.