What really helped me improve my typing speed is... learning to touch-type, instead of hunt-and-peck.

But QWERTY is too crazy to learn, except by osmosis. So instead I decided to learn Dvorak, which is logical, and efficient (for English at least). It took me only 2 weeks to learn it because it makes sense, and then after one month I was back at my old hunt-and-peck speed. Now I can type around 70-80 WPM with 90-95% accuracy.

But that was never really my aim. I just wanted the shooting pains in my arms to stop, and was too cheap to get an "ergonomic" keyboard. Dvorak really helped me there.

When my fingers hurt after too much time on the keyboard, I.... Wait. That never happens. I don't type QWERTY, so my fingers don't have to do weird contortions.