For the past couple years I've been dealing with repetitive strain injury (RSI) in both my wrists (well forearms really). It's been quite frustrating to deal with and taking long breaks from extra curriclar work (comics) just depressed me and didn't help much. Here are some things I've done that have helped - I should note that from reading stuff online it seems that no two instances of RSI are the same - so keep that in mind.
*Ideally you avoid these measures by always taking breaks (see number 4 below)
1. Doctor / Physiotherapist - I went to both a doctor and a physiotherapist. They ruled out carpal tunnel and tennis elbow and set me up with some stretches.
2. Braces - When I draw or use a computer I wear a wrist brace like this
Its ugly and gets uncomfortable - but it really helps the tendons. When both wrists were bad I wore them on both hands. When my whole arm was feeling bad I would wear an elbow brace as well. Thankfully, I'm down to just one brace on my drawing hand.
3. Stretches - I've tried a whole bunch of things. I kept up a good regiment with these stretches - but ultimately found they didn't help a lot. I used a resistance band to strengthen my wrists for a while, but eventually ditched the band in favor of 5 pound weights.
I do repetitions as in the above video EVERY morning, first thing before I draw. I actually keep the weights next to my drafting board.
4. AntiRSI software - This application has made a HUGE difference. It monitors your keyboard and mouse (or tablet) input and forces you to take micro breaks (I have it set to 12 seconds every 4 minutes) and full work breaks (6 minutes every hour). It can be very annoying to have to stop but the benefits far out-way the annoyance - and it's free!
5. Fat Grip - Scott McCloud's post on this very subject matter has this at number 1. And with good cause. I've got all my tools taped up and it is way more comfortable. Try it out!
6. Avoid Touchscreens / videogames - My wrist pain is really a result of very small movements of my tendons. I can place tennis with no pain at all, but scrabble on the ipod touch had to be deleted. Videogame controllers are also bad news. I spent a month paying for one night of COD with the guys. Lesson learned!
There are more things I've changed - and I will probably get around to writing about this subject a bit more in the future.