Communal Living

Different communal living spaces have different sets of rules in relation to who is living in the area and who has more "power" over the area. For example, living in a house with my parents, they call all the shots and decisions about who comes in and what is done with the space is ultimately up to them; it's their house. On the other hand, living with a roommate in college is different-- equal. At least in the dorms it is because you are both paying the same amount to live there. In off-campus housing, roommates may split things differently depending on how much rent each one is playing.
One of the most important things about living with someone else seems to be, in my experience, privacy. You should always respect the other person's space and things. There should always be some sort of between who gets what, and who pays for what, or who cleans what, otherwise resentment will arise out of the person who feels like they are doing more than the other. There should be some discussion as to what sort of furnishing and decorations the house or apartment will get, or mutual understanding of what the other likes. To be honest though, my roommate and I will take anything we can get.
Because we are in school and have jobs, respecting one another's time and sleep is important as well. For example, inviting friends over the night before your roommate has a big test probably isn't the best idea. Living in a communal area comes down to BALANCE. It doesn't always work out, but hopefully if you treat someone the way you would want them to treat you, they will do the same.