It's a rare college roommate situation where neither person brings over a guest at any time during the entire academic year. More likely, one or both roommates has someone over -- for the night, for the weekend, for a day or two. Having a few basic rules in place in advance, however, can help everyone avoid awkward situations, hurt feelings, and overall frustration.
Rule 1: Notify as far in advance as possible. If your parents are coming to visit for Family Weekend, let your roommate(s) know as soon as you can. That way, the room can be clean, things can be picked up, and embarrassing items can be put away if necessary. If your guest shows up as a surprise -- e.g., your boyfriend drives up to surprise you for the weekend -- let your roommate know before they come home. A simple phone call or text message can at least give them a heads up that you'll be having company for a little while.
Rule 2: Know what's okay to share -- and not. Most roommates don't mind if you borrow something from time to time. A squeeze of toothpaste here or some hand soap there won't bother most folks. A used towel, eaten breakfast food, and laptop surfing can easily send the calmest roommate into orbit, however. Know what your roommate is willing to share and let your guest know as soon as possible. Even if you're in class while your guest eats the last of your roommate's cereal, it's your responsibility to fix the problem.
Rule 3: Have a limit on how long people can stay. It's reasonable to expect a roommate to accommodate the unique factors of your personal life. Your mom might call too often, for example, or you might have an annoying habit of hitting the snooze button one too many times in the morning. Having a guest stay for too long, however, is not something you can reasonably expect your roommate to adapt to. It's their place too, after all, and they need their regular time and space to focus on school. Respect your shared environment and make sure your guests leave before they overstay their welcome.
Rule 4: Make sure your guest leaves things exactly how he or she found them. If your guest wants to be a good house guest, they should be respectful of everything in your shared living environment. That means cleaning up after themselves, whether in the bathroom or the kitchen. The last thing you need is for your guest to be disrespectful and leave a mess behind. Ask your guest to make sure to clean up after him- or herself, and if they don't, make sure you do as soon as possible.
Rule 5: Be clear on how frequently guests can visit. Okay, so all of your guests are dreamy. They don't stay too long, they tell you they're coming in advance, they clean up after themselves, and they respect your roommate's stuff and space. That can all be true, and yet ... you can simply have guests over too often. If people are over every weekend, for example, that could easily become wearisome for your roommate(s), who might simply start craving the ability to wake up on a Saturday morning and not have to deal with company. Talk to your roommate not only about guest specifics but also about patterns. How much is too much? How many is too many? Being clear from the beginning and checking in throughout the year can make sure that you and your roommate continue to have a good roommate relationship -- guests and all.