If you really want to get the scoop on whether a contractor is the right fit for your project, make it a point to contact some of that contractor's recent customers.
There are three questions you should ask: What kind of work did the contractor do for you? Did you have a clear idea of what the contractor was going to do? And did you check the contractor's credentials?
Angie Hicks of Angies List says, "When speaking with the reference be sure to ask open ended questions. Don't ask just yes and no questions because then you are really going to get them talking and you can pick up tidbits about the experience."
No one answer will say more about a contractor's work than the customer's willingness to hire them again. If they aren't willing to hire the contractor again, ask why not.