When my fingers hurt after too much time on the keyboard, I... take a break and relax for a few minutes then i get back to typing so I can finish what I need to do.

My tip to improve your typing speed is to make sure that when i type that I constantly over look my sentences to make sure that what i have typed is what I want it to be and I didn't make any mistakes. I not only do this when i type but when I am texting on my phone or other wise.