You may have a vision of you and your roommate sharing secrets, clothes, jokes and souls. I hate to break it to you (actually, I enjoy shattering naïve dreams) but that's probably not going to happen. You probably won't hate your roommate, but you guys likely won't be besties either.
Lower your expectations before you get to school. If you come to campus positive that you and your new roommate are two halves of some long-ago torn-apart soul, you're setting yourself up for disappointment. Instead, shoot for a good relationship, where you're both honest about your needs and expectations. If you end up being friends, great. If not, you won't have front-loaded the relationship with all sorts of hopeful baggage that you'll have to get rid of at a later time.
Also, if you want to be best friends and your roommate doesn't, don't go around trying to steal his or her life. Leave that to the horror movies. And if your roommate is trying to steal your life (styling her hair the same way, getting the same tattoos, drugging your boyfriends and sleeping with them, referring to herself as your twin and so on), talk to your resident advisor.