Patti Wood has had her share of awful roommates. When she was in graduate school, she interviewed a woman who seemed prim, proper and very studious. But Wood forgot to cover a critical topic. “I didn’t ask what she was going to bring into the space,” says the Atlanta-based expert on body language and interpersonal communication. “She brought 20 to 30 plants and four wind chimes — I felt like I was in a science experiment.”

Millions of Americans seek roommates every year, and in today’s tight economy, the number of people relying on a roommate to share expenses will likely grow. If you’ll be launching a roommate search soon, do your legwork up front to avoid grief on the back end.

Aaron Loring Davis, an agent with Sotheby’s International Realty in Los Angeles, helps people find homes by day and lives with roommates by night. Davis starts his screening process by asking potential roommates to answer a few questions. “I preface the request by saying, ‘Please answer all questions,’” he explains. “I ask people where they work, why they’re moving and what they’re looking for in a roommate. People who don’t answer all the questions are out. I’m not going to get into bed with somebody who isn’t going to follow through from the outset.”

Be equally inquisitive when you meet people in person. To identify potential conflicts, ask how often they’ll have people over and whether their guests will spend the night. “I’d also ask about their sleeping and waking habits,” advises Wood. “When do they wake up in the morning, and what’s their ritual? Some people blare the TV when they’re getting ready. Others let their alarm go off for a long time. Those nonverbal things can interfere with your comfort.”

Davis also suggests that you both be honest about deal-breakers. That technique has led prospects to pass on sharing a home, but that’s fine with him. “I have friends from all over the world, so I’ve asked, ‘Do you have any issue with a friend staying on the couch?’” he explains. “Some people said they weren’t interested in having other people stay in the house. It was refreshing to have that discussion.”

Don’t ignore non-verbal cues. “A potential roommate in grad school couldn’t make eye contact,” says Wood. “I blew it off and thought maybe he was just really shy. When he moved in, he barely left his bedroom and moved out in the middle of the night. Tune in to your intuition, and if something’s bothering you, pay attention. Otherwise, it’ll come back to haunt you.”

Finally, investigate a potential roomie’s track record. “Verify their information as if they were going to be renting from you,” recommends Maurice Ortiz, managing director of Apartment People, a rental agency in Chicago. “Run a credit check, verify their employment information, and call past landlords to make sure they’ve paid their rent on time. You may even want to do a criminal background check.”

If people try to smooth-talk you out of these checks, run like mad in the other direction. “It’s better to be safe than sorry,” says Ortiz, “because you’re going to be stuck with this person for a year.”