I practice typing in English with TypeRacer since my wpm was around 30'ish. Now my wpm is 80+ in Colemak and around 40-50 in Qwerty.
Rule of thumb : Don't look at your keyboard, this waste you around 1 second each time. So remember all the keys.
Aim for accuracy rather than speed.
Reduce subvocalization : This is quite similar to reading technique. If you can't force yourself not to spell words you typing, try read it in words. It is still better than reading each alphabet.
Read ahead : I made userstyle for 10fastfingers to force reading a word ahead. I think this technique is necessary to break the 100wpm wall. This method is not well known.