What really helped me improve my typing speed is playing piano and doing typing/scale exercises when I was in high school (repetitive for finger strength). I - and this is probably bad - crack my knuckles, stretch out my fingers, warm them up, wiggle them around.

My tip to improve your typing speed is to only look at the screen. Try not to correct too many simple mistakes if you don't need to or if they are too far back. Get quick at "delete."