Get to know your roommate before you move in
You don't necessarily have to be friends to move into the dorms together. In fact, most roommates don't even know each other. This provides a great experience in learning how to live with other people in a positive environment. If you don't already know your roommate, be sure to contact them before you move in together. Be sure to talk to them on the phone or in person if possible. You may be able to find them online, but perceptions can be misleading on the web. Most Schools provide you with your roommates contact information before you move in for this purpose. It is also helpful to figure out who is bringing what so you don't end up with two of everything and no space left. Some good items to talk about sharing are Televisions, microwaves, micro fridges, and extra furniture.
Set up guidelines right away
Most dorms also offer roommate agreements. This is a paper that you and your roommate fill out talking about cleaning, sleep schedules, guests, sharing items, and other common areas of conflict. Be sure to add any additional things you want to agree on. If your community does not offer roommate agreements, don't be afraid to make your own. Address who is going to clean the common areas, when the noise should be kept down, when guests are allowed over, what you will share and keep separate. Be sure to tell each other of pet peeves and write up a contract. Make sure all roommates sign, and put it in a place where you both can find and refer to.
Don't shrug off the little things
Often, the biggest roommate conflicts arise because of one last straw that "broke the Camel's back". If your roommate does something that bothers, or upsets you, be sure to address it right away. The more little things you address in the beginnig, the less likely they will turn into more serious issues.
Hang out with each other
If you and your roommate become friends, be sure to hang out with them at times outside of the room or apartment. Sometimes something just as simple as going grocery shopping together can relieve tension and help you to stay friends outside the halls. If you and your roommate do not become friends, try to find time to spend with them to talk about your weeks, and any issues that may be on your mind, no matter how small.
Take advantage of open room changes
Just like classes, and books, most university's have an open room change policy the first week or two. This means it is a small amount of paperwork involved and you can do it hassle free. This is an option if you start meeting other people around you that might have similar interests or living styles. However, be sure to talk with your current roommate to make sure they are okay with a room change. Maybe they had a friend in mind as well, or they might have become accustomed to you as their roommate and be upset. No matter what, be sure a roommate change is OK with everyone involved.