Be careful with your body. Believe me, I speak from experience.
Around 2003 I started experiencing acute pain in my right wrist. I tried ace bandages, neoprene gloves, creams, etc. It got worse and worse.
Finally, I had to admit I was getting to the point when I would not be able to make my strip anymore, and so I got a tablet. I also learned to mouse with my left hand, something that is not only annoying but also takes some while to get accustomed to.
You see, my problem was that I was shading with my mouse. That’s VERY movement-intensive. I’m happy to say that since I took those two simple measures, I no longer suffer from carpal tunnel. Or at least, I nipped it in the bud before it gave me a permanent injure that required surgery.
This is a pretty stupid thing to say in a blog like this, but I have seen it again and again. People, take care of your hands, especially the one you draw with. Most people in the world are extra careful with their eyes, well, it’s not so hard. I have stupidly injured myself doing everyday things, and I’m afraid it could have been avoided. I hear a lot of people saying they smashed their fingers using a hammer to hit a nail… why??? Why doesn’t anybody use pliers to hold the nail into place? Why do people keep peeling potatoes without holding them using a napkin? Why do people keep touching the iron to see if it’s already hot??? Okay I only did that once, gimme a break 
Choose a chair you feel comfortable in. Allow yourself to put your feet up and prop back from time to time. You’ll spend a lot of time in your chair so consider it an investment. You don’t want to save on a chair and spend on a chiropractor.
Make sure your chair is at an appropiate level with your table. Do NOT force your wrist, either up or down, the straighter it is, the less damage you do. Consider wearing an ACE bandage while working, at least for a while (you can create an habit by that)
I have tested a lot of surfaces to run your mouse in, and so far nothing equals a straight sheet of normal printing paper. Yeah, mousepads suck, even those who have boobs. Sorry, Japan.
I recommend optical mouses, but I don’t recommend wireless ones. They’re not worth it, IMHO, they take too many batteries. Now, wireless keyboard is very useful, especially if you’re running a two-monitor system.
Avoid spending a lot of time typing in those tiny laptop keyboards. They’re horribly uncomfortable.
Move your feet around for better circulation, you’ll get less tired if you do that.
Finally, LISTEN to your body. If something’s not working for you, be it your monitor, keyboard, mouse or tablet, it doesn’t matter if you spent a lot of money on it. Your health and comfort are way more valuable! Especially if you’re in this for the long run.