I have some pretty fail-safe roommate etiquette tips from my experience with many roommates. It all starts around a pretty simple yet powerful concept/office supply: masking tape. From my experience, most run-ins with roomates happen because of ambiguity. "Which side of the room am I not allowed to step in?" "Which side of the counter is it best I keep my things off?" etc. If roommates would make a simple practice of masking off sections of the apartment/counter/fridge/etc. to designate each roommate's "space" numerous fights would be prevented.
I can sum up my remedy for most roommate squabbles in one word: labeling. Labelling is really the Godfather of masking off areas: the idea is to designate ownership or personal property/space. Labeling takes care of the vast majority of roommate problems, ("You can't use my ruler." "How do you know it's yours?" "Because it says so on the label.")
But even after extensive labeling, I also find it helpful to make a few lists. In my experience, I have made numerous lists, they usually differ with each new roommate depending on what his annoying (or non-annoying as the case may be) habits, but here are some lists that seem to recur with some regularity: List #1: food items that my roommate can't eat no matter how hungry he or she is (like any food that is labelled, and like Doritos). List #2: food items that it is unfair for roommates to put on their list #1 because I really like them (like Pringles). List #3: things that really annoy me (like snoring). List #4: things that it is unfair for roommates to put on list #3 because it's just how I am--or I'm working on it (like smelling bad, or taking too long in the shower). I find that after I live with a particular roommate for a little while, it is usually worthwhile to add a couple other lists, but they differ from roommate to roommate, but I have probably made around 28 different lists.
Next, I think it is really important for roommates to get together regularly to discuss their relationship. I find it helpful for me to document things that I might find annoying. It can especially be helpful to put it in an organized (Powerpoint?) presentation to communicate the issue. But this can hurt feelings, so it is really important to tell the other some positive qualities that he or she has (You are so thoughtful--and smart! Hey you! You rock-star hero! I love how you clean up after yourself!) This is also an opportunity to express appreciation (I noticed you haven't been snoring as much, I really appreciate if you have been taking those snoring pills I gave you.)
Finally, where possible, see to the spiritual development of each roommate. This is a special time in your life! Remember that! Never forget that each of you is a valuable child of God. Each roommate! And remember that you will be glad for the effort you make to help each other make the most of your time and be happy.