Make sure your potential roommate has lived with roommates before. I've lived with a few girls who all came from living at home/in their own dorm room and I could definitely tell the difference. Three important things I'd say:
1. Conscientiousness. Seriously, the most successful roommate relationships I've had are with people who respect your space (keeping common areas clean) and know if they're being a burden (music too loud/ SO staying over frequently)
2. Cleanliness. Doesn't bother everyone, but it bothers me. There is a difference between MESSY and DIRTY...I don't want to come home to dirty dishes every day, but I don't want my roommate to chop my head off if I leave a book or two lying around. Just make sure you're on the same page.
3. General safety and finances. They will pay rent on time, lock the door, pay utilities, etc. Pretty self explanatory.
Hope this helped! I've had a LOT of different living arrangements and lived with a ton of people, almost always successfully.