1) Do what your teacher asks you to do. Complete all assignments to the teacher's exact specifications. Come prepared to class. You know you need a writing tool no matter what. How about some paper? And of course, your completed homework does no good sitting on your desk at home.
2) Show you care about the class even if you don't. Sit near the front, avoid distracting classmates, sit up straight, and make eye contact. Listen for verbal clues, and watch for non-verbal clues. For those less engaging classes, make sure you get enough sleep; nodding off is a big no-no.
3) Ask questions and contribute to the class discussion. These show your teacher that you are grappling with a particular subject and are synthesizing new information. Make sure you are paying attention to what is being said by classmates so you don't repeat it. Reference their contributions in your own words when appropriate. However, don't talk just to hear yourself speak or become the obsequious kid that even the teacher avoids calling on after a few days.
4) Make sure everything you submit, by e-mail or on paper, is in pristine condition. Proofread your work and be certain that it makes sense. There should never be spelling or grammar mistakes. And it goes without saying, no juice stains, no creases or folds, and no teeth marks (canine or otherwise).
5) Be on time. There's no easier way to impress than by being in your seat, ready to learn, when the bell rings. There are few things more glaring than interrupting your teacher midsentence to do the "walk of shame" from the classroom door to your seat.