Living with other people is tough, especially if you've never had to share a significant amount of space with another person before. You need to be aware of other people's wants and needs and keep in mind that you may need to compromise on things you're not used to having to compromise on. However, being a good roommate really isn't that hard, not if you follow these easy steps.
1. Communicate clearly, right from the start.
Be clear about what you expect to get from living together. Be clear, but not unreasonable. If something one of your roommates does makes you uncomfortable, say so. If something one of your roommates does makes you irritated, maybe pick your battles and learn to get used to their quirks. If you feel as though your space has been invaded, speak calmly and politely about it. Know when you start and argument and when to let it go. Some things just aren't worth creating tension over.
2. Understand boundaries.
If a door is closed, knock. If you want to use something that isn't yours, ask first. If one of your roommates isn't the touchy-feely type, don't be going in for the hug every time you see them. You all might be sharing a space, but it's important to understand that that doesn't mean you are sharing everything in that space. You each have areas and property that belong only to you, and it's important to be respectful of that.
3. Clean up after yourself.
This one should be a no-brainer; but for some reason, it just isn't. Don't leave your dishes in the sink long enough to grow something. Don't leave all of your books in the living room. Keep your mess confined to your room and not the common areas. Everyone should feel comfortable entering shared spaces.
4. Be considerate.
If your roommate is taking a nap when you get home, maybe go to the dining hall instead of cooking a three course meal in the kitchen. Lower the music at night if one of the roommates goes to bed. Ask before moving furniture in the common areas or reorganizing the kitchen cabinets. Think about what you hope your roommates would do for you, and try to do that.
5. Be kind.
If your roommate is sick, offer her your box of tissues. If one roommate had a bad day, put aside your work long enough to ask her about it. If you're loading the dishwasher, put your roommates' plates in too. It's the little things that really make for a cohesive living situation. Going out of your way to show a little kindness to your roommates--even if you aren't best friends--goes a long way in creating a comfortable and safe living environment that you feel good coming back to at the end of the day.