Dorm mates aren't the only people to use dorms. Crowded though it may be, the room may host study sessions, meals and parties. Make sure your visitors know the house rules regarding privacy. Keep an eye on younger siblings and other children who haven't yet grasped the concept of privacy. Don't be shy about enforcing a roommate's rules, even if you or your friends don't understand them.
Having friends over can also require a special set of rules to prevent potential invasions of privacy. A roommate who's an early riser may not want friends phoning at 11:30 p.m. Ask roommates how they feel about visitors sitting on their bed or browsing through their books. Again, you might make certain allowances for the demands of friendship. If your friend asks for a snack before rushing off to work, you might give her a carton of your roommate's yogurt. But just be sure to replace it as soon as possible, with a few more cartons as interest on the loan.