My tip to improve your typing speed is to make sure that you slow down when you feel you are about to mistakenly type a word.

Slowing down by half a second per word to give yourself the time to think and prevent writing errors is much faster.

Blazing through, realizing you've mistakenly typed a word, backspacing on average 5 to 6 times to correct it, thus moving your fingers from your natural typing position, only leads to more errors, more time spend fixing those errors and a generally slower typing speed.