1. Opposites may make great friends, but not necessarily great roommates. That cool chick who "brings out your wild side" may not be the best choice as your roommate if you are normally quiet and introspective. Be completely honest: Do you share a passion for neatness? Is one of you a night owl? A smoker? Make sure your lifestyles are compatible.
2. Would you loan this person the monthly rent? If your roommate can't pay his share of the rent, you'll have to cover it or face eviction.
3. Your roommate's screw-ups can cost you your tenancy. The landlord can evict all of you for the wild party your buddy held last weekend, even though you were out of town.
4. Be nice to your parents. Landlords often ask student renters if their parents will cosign the lease, meaning the landlord can demand rent from the parents if the tenants don't pay. If one set of parents cosigns a lease, all parents should, so no one is stuck paying rent for someone else's kid.
5. "Who moved my cheese?" is not just a popular book. It could also be a troubling verbatim comment out of your roommate's mouth. Find out about your roommate's obsession with food and other quirks before you move in, by checking with her past roommates. Give her the opportunity to check out your bizarre habits, too.
6. Have a frank discussion about overnight guests. A girlfriend who becomes a nightly fixture may as well be a tenant—but she's not paying rent. Worse, you could get evicted for having an unauthorized occupant (someone not screened and approved by the landlord like you were).
7. Create a system for splitting and paying bills, such as electricity, phone, and cable. If you're writing checks for shared bills, make sure the other roommates pay you before the bills are due. Otherwise, you guessed it—you're fronting another loan.
8. Agree what will happen if someone wants to leave. How much notice will that roommate give the others? Will the departing tenant be responsible for finding an acceptable replacement?
9. Prepare for a breakup—what if some of you want a roommate to leave? (If couples can anticipate the end with a prenuptial agreement, you can, too.) Consider agreeing to use a landlord/tenant mediation service, which you'll find free in many cities.
10. When you move out, the landlord will use your deposit to pay for damage and needed cleaning, and he won't care a bit about which roommate was responsible. It's up to you to apportion the responsibility—and divide the returned deposit among yourselves accordingly.