Treat them how you want to be treated!
#1 Be clear from the beginning.
Discuss with your roommate any habits/quirks you have and find out theirs so it will save your roommate and you from future arguments.
#2 Be open to change.
Learn to grown and change during your time at school and realize things will be different for both of you.
#3 Focus on behavior, not personality.
Instead of getting annoyed with your roommates quirks that bother you, focus on the behavior and how it affects you. and nicely request to modify the behavior.
#4 Call, dont click
Once you've been assigned your roommate its okay to look them up online, but dont judge them from what you see on the internet, talk to them over phone or in person about it to understand their side of it.
#5 Be friendly, without expecting to be best friends.
Don't go into your roommate relationship thinking you and your roommate are going to be best friends for the entire time at school. You should be friendly with your roommate but make sure to have your own social circles.