Just do the work on time or ahead if time and don't be afraid to ask questions. If the class you want to take has multiple classes with different professors use ratemyprofessor.com and look through the comments to choose the best one. I've saved myself from some awful teachers that way. Above all Don't Panic! I've seen people crash and burn from freaking out over midterms or finals. I used to throw a big house party just before finals to ease all my friends tensions