I set myself a goal speed, like 90WPM, and whenever I don't meet that speed on a test, I click on the title and train on the quote until I either reach that speed or do the test five times. That way my fingers get accustomed to whatever made me mess up more or get slower on the quote. It's way better than just dreading any time a quote comes up with keys I'm not good at. Practicing the same quote over and over also helps my fingers "memorize" certain combinations of keys so they can perform them without me having to think about it. The more combinations my fingers know, the faster I can type.
I also make sure that I'm using the right fingers on the right keys. The more you practice pressing a key with the wrong finger, the stronger the bad habit becomes. I intentionally slow down and make sure I'm typing the right way every once in a while.