Your wrists should not be in contact with anything while you're typing.
Ergonomic keyboards are ok, but a correct typing position will make more of a different than an ergonomic keyboard. Of course, both will help - an ergonomic keyboard gives you a more natural angle of attack.
I've just googled and found this: 10 Simple RSI Prevention Tips Seem good advice.
If you want to join the keyboard elite cr0sh is right, model M is the only way to go.