How to get the benefit of the doubt from your instructors...
1) Never try to lie to them. They may not be able to prove you've lied -- but, they'll suspect it and suddenly they'll enforce every little provision in the syllabus.
2) Come to class -- all the time, unless you actually ARE sick.
3) Be prepared for class -- or, at least be prepared enough to ask a decent question or bring up an interesting point. Also, keep your electronic stuff turned off during class... cell phones, laptops etc. are for before or after class.
4) Turn your stuff in on time, proofread it etc. We want to see that you're making an effort. IF we make note of a mistake on one assignment, correct it for the next time. If we are generous enough to take a revision, make sure the revised paper is perfect!
5) Be respectful, both to your instructor and to your classmates... even if they are complete idiots, take the opportunity fake respect. This is a very important job/life skill -- because you'll be working with idiots and you'll need things from them.
That way, when crap happens in your life, your instructor will be more inclined to give you a break.
I'm thinking about this because I just gave a huge break to a student who has consistently managed to do #1-5. Not doing so would have hurt her grade, but she earned it!