The #1 piece of advice: Do a credit check! Its cost is minimal compared to the cost of what could happen if you get a bad tenant.
#2: Never, ever contact a prospective tenant's existing landlord.
Contact previous landlords. If this is a bad tenant, the existing landlord likely wants to get rid of them.
#3: Knowing what to ask, and the language you use to ask a question, is incredibly important.
There are questions landlords should and should not ask prospective tenants in order to keep on the right side of the law.
By asking very open-ended questions, such as “Tell me about yourself,” the prospective tenant will tell you perhaps a lot you need to know in order to make your decision.
There are ways to stay on the right side of the law and still get the info you need. While you can’t ask an intrusive personal question like “Are you planning to have any more children?” you are allowed to ask: “How many people will be living in the unit? What are their names?”
Adapted from Canadian Real Estate Magazine