I, too, experienced this. I feel like the most important thing is to establish rules right away, if only for the sake of privacy and the respect of each other's space, especially since dorms are usually small.

As the above poster said, always keep things clean. Don't give them any reason to get on your case for stuff lyin' around and all of that. Chances are that even if you don't get along as friends, you still won't turn out to be enemies. Be honest and let them know that you have reservations socially at the very least, and that should make things easier, so they don't think any of your behavior is personally directed at them, or that you're giving them the cold shoulder or something like that.

My roomates and I were all strangers to each other with very different backgrounds, but by setting respectful rules beforehand and getting in any pet peeves or quirks about ourselves (ie "i hate towels on the floor!" haha) out on the table, living was good. Mutual respect is just really important.

I ended up becoming really good friends with one of them...who is totally the opposite and very social, etc! The other...well...she literally had depression, OCD, ADHD, shopping addiction (spoilllled!!! Daddy put college on his credit card, and everything else she wanted), liked to add massive amounts of alcohol and some drugs to this mix...and never took her meds. She was famous for basically being out of control in our building. People would say to us, "Wait...You guys are roomates with Michelle? ...Omg. I'm so sorry." Or "...How is that?" Luckily, that's what campus security and housing management is for! Obviously, this is probably one of THE most extreme situations.

But, again, even with this craziness, respect won out - after my friendly roomate and I made it starkly clear that we were fed up with Michelle and with her full knowledge reported her to student housing, she was remorseful for the rest of the year and just neutrally left us alone. Boundaries, boundaries, boundaries - and stickin' to 'em. We didn't let her behavior just slide.

Also, most colleges offer some mental health counseling for at least a few sessions, or just regular student counselors that are happy to talk with you and listen to you vent or get you some help or tools if you ever need or are just feeling uncomfortable or stressed. So even just for the first few weeks, maybe when you get there you could set something like that up, just so you know you have some support.