From the other side of the fence, that is, the person who has another room in their house or apartment they'd like to rent, there's a few tricks I've found to getting a good roommate. I hope you can learn from my mistakes. Note: I live in a very tight housing market, so I can afford to be choosy. You may not, in which case these wouldn't be the smartest thing to do.
- Create a Fantasy Person Who Saw the Apartment Yesterday
When you show the apartment, if the person likes it they will automatically assume you want them to move in. This isn't necessarily the case. Remember, you're going to be living with this person for an extended period of time. Be selective. If you have this "person who has the first dibs on the apartment" -- or any excuse like that -- it relieves you from telling the prospective roommate that you just don't like the look of them.
- Get to Know the Prospective Roommate
This is really important when paired with the first point. Have a long chat with the prospect. Casually slip in questions about where they're from, what they do, etc. The point of the conversation is to get a sense of this person's employment and tenancy habits (if they say something about moving every 6 months to a new city, do you really want them living there?). You can also slip in some of your expectations for the eventual tenant. (For instance, if they recoil in shocked horror when you say, "I'd like the kitchen to stay pretty clean," this may not be the ideal tenant.)
- Make a Good Sign & Think About Where You Place It
Go ahead and include stuff like "looking for clean non-smoker" if that's what you know you'll want. Sure, you might have only 75% of the calls you might have got without looking like an anal-retentive, but you want to weed those people out. Then, put it up where you know you'll get the "right" people (boy, I sound like an elitist). If you don't want some college kid getting his first apartment out of the dorms, don't put a sign up in the student union.