Wrist rests are evil. I'm convinced that they're what cause typing and mouse-related RSI 90% of the time. Just learn to type with your wrists loose but at a neutral angle. Yes, your arms will get tired after a while, but that just means that it's time to get up and do something else for a while anyway.

My mother was a professional typist for many years — at least 15 — and I never knew her to have any wrist pain or espouse any physical recommendations beside just holding your wrists properly. And by "professional typist", I don't mean "secretary". She transcribed court cases and 90% of her job was typing. And on a real typewriter; not these low-pressure mush-boards we have now. In fact, I use a mechanical keyboard, mostly because I like how they feel, but it has been suggested that the way one types on a mechanical keyboard is better for you than on a membrane keyboard because you don't end up bottoming out on the key; you actually press less hard, despite the fact that the pressure required to activate the key is actually more.