My tip to improve your typing speed is to strive for 100% accuracy. Every. Single. Game.

When my fingers hurt after too much time on the keyboard, I put my hands in the air and wave them like I just don't care.

My tip to improve your typing speed is to remap your keyboard's caps lock into a backspace key. It saves a lot of movement and is therefore faster and less stressful on your hands. I recommend SharpKeys as a good remapping program.