1. TAKE BREAKS!
Be sure to take breaks from using your computer. Every hour or so, get up and walk around, get a drink of water, stretch whatever muscles are tight, and look out the window at a far off object (to rest your eyes).
2. Practice good posture.
If you can't hold good posture, it probably means it's time for you to take a break from typing. If you are perpetually struggling to maintain good posture, you probably need to adjust your workstation or chair, or develop some of the support muscles necessary for good posture.
3. Use an ergonomically optimized workstation to reduce strain on your body.
4. Exercise regularly.
This includes strengthening, stretching, and aerobic exercises.
5. Only use the computer as much as you need to.
Think before you type to avoid unnecessary editing.
6. Don't overstretch your hands for the hard-to-reach keys.
e.g. BACKSPACE, ENTER, SHIFT, CONTROL... basically everything but the letters. Instead, move your entire hand so that you may press the desired key with ease. This is crucial when you are programming or typing something, where non-letter keys are used extensively.
7. Let your hands float above the keyboard when you type
and move your entire arm when moving your mouse or typing hard-to-reach keys, keeping the wrist joint straight at all times. (The correct position is shown in the diagram above)
8. Use two hands to type combination keystrokes,
such as those involving the SHIFT and CONTROL keys.
9. When writing, avoid gripping your pen too tightly.
10. Realize that you are not invincible.
RSI can happen to you. Don't be afraid to ask for help.