You've found an apartment and need to find a non-scary, non-smelly, hopefully-quite-clean someone to share it with. How do you start? Send an email to your network of friends and colleagues. Maybe one of them is looking for a change, but hasn't made the news public yet.
If that doesn't work, don't go contacting a psychic or putting up fliers in coffee shops yet. There are online services and websites you can try. Sites like roommates.com offer profiles, searches and matches to help you find a potential new person with whom you can share that sweet loft apartment you saw yesterday and can't stop thinking about.
Once you've found someone who seems like a good match, discuss each of your lifestyle and roommate preferences. It won't take long for you to realize that life at the bank isn't going to mesh well with a guitar-playing roommate in a punk band, no matter how much your sense of humor mesh.
Also, make sure your potential roommate is verifiable (not certifiable). Get references, put him/her on the lease, get a deposit for his/her share of the rent. You don't want to be responsible for Roomie's rent, if your instincts failed you this once and you come home to a half empty place one night (let's hope Roomie's half is the empty one). Relax. That's not going to happen. But just in case, it doesn't hurt to be prepared.