Best advice I can think of is to do whatever it is you do in class at home--repeatedly. Whatever kata or drills you have, go over them constantly. When you catch yourself doing something improperly, correct yourself. In the dojo, your improvements should start to show, and your teacher can start correcting you on new problems. The bad habit will break-- it just takes time and lots of repetition.
David Sims
"Cuius testiculos habes, habeas cardia et cerebellum." - Terry Pratchet
My opinion is, in all likelihood, worth exactly what you are paying for it.