1. Have the client fill out an application - Checking and calling all of their references.
2. Require full payment of rent prior to move in (keep in mind that money orders can bounce).
3. Collect a larger security deposit.
4. Google the company and individual's name.
5. Check social media sites like Facebook, Linkedin and twitter.
6. Check out beenverified.com. Most importantly have a conversation with them and prepare a list of questions to follow. This will help give you a level of comfort about their viability as a tenant allowing you to make an informed decision on their on their tenancy.