One of the most tempting steps to skip in hiring is checking references. You go to all the trouble of actually getting ahold of someone and all they say is “Yes, he worked here for those dates.” Still, it is important to do the leg work and, with luck, find a reference who will actually tell you something useful.
Look at the references the candidate gives you. Are they real supervisors from previous companies? or someone they “worked with”, maybe a friend? Are they willing to list supervisors or bosses from all their previous jobs? If not, why not?
You can ask for additional references, especially clients/customers. Ask the candidate for their “most difficult client” and contact them; if the client gives the candidate a positive reference, that is a good sign. Alternatively, ask for the most difficult boss. Those references will tell you a lot about the candidate’s ability to deal with difficult people and stress.
If you want to talk to the candidate’s current boss or clients, get authorization from the candidate first; they may not have made their move public yet. For positions where the candidate is no longer working, no authorization is needed.
One question that most people will answer, and that gives you a surprising amount of information, is “Would you hire her again?” You might get a scripted answer like “She is eligible for rehire”, which still tells you that they left under decent terms and didn’t break any major rules at that job. With luck, you will get some inflection in the reference’s voice; “I would hire him again immediately!” is quite different than a flat “Yes.” Try following up with “why or why not?”
If they aren’t eligible for rehire and you didn’t know that, then it is worth a conversation with the candidate, especially if the reference won’t say anything more. This is where you might be able to pick up the kinds of issues that aren’t apparent but that can come back to bite you later, like a theft record. There is no guarantee that you will, but at least you will have made a good-faith effort to do so; that will look a lot better than negligence if you have a problem in the future.
Last, make the calls yourself; don’t pawn them off on the 20-year-old receptionist who has no idea of what to listen for. You will hear what isn’t said, and sometimes that is more enlightening than what is said. This is your chance to get a better idea of what kind of employee the candidate is likely to be, so take advantage of it. Making those calls is so much easier than having to fire someone in three months!