Even if you've followed all the hiring advice we've covered so far in this series, there's another critical step before you make an offer: You've got to talk to the people who've actually worked with the candidate.

Cutting corners when it comes to checking references is flirting with disaster. Sound obvious? You'd be surprised how many executives treat reference checking lightly, or skip it altogether. Reference calls are not a "check the box" hiring chore to get quickly off your list.

Take them seriously and do them yourself, rather than delegating to HR or an assistant. (You can get help verifying references' positions, histories and employment dates, if you need to.) What a person has done in the past, and the type of character and heart they have, are the best predictors of what they'll do in the future - and the people that have worked with them can give you the clearest picture of these qualities, if you ask the right questions.

Here are some best practices to consider:

• Don't call references out of the blue. Arrange for interviews at a convenient time; and thank them in advance for their help.
• Be as friendly as possible on the calls, and let the person know the conversation will remain confidential.
• Have some standard questions, but make sure the conversation is open-ended - you are, after all, trying to get the reference to open up. (That said, don't ask questions about, or make comments on, the candidate's personal life.)
• Employ a 'grain of salt' mentality when you're calling references the candidate provided. These 'primary references' will nearly always give the candidate a good review. Still, they can provide insight into her tendencies: Does she like working independently or on a team? With lots of feedback or without much supervision?
• Don't stop with primary references. Get a second set of references from the first references; and if you need to, seek a third set from the second group. You can do this by asking a supervisor to suggest a colleague with whom your candidate worked closely. And that colleague may suggest another colleague. The further you get from the candidate's "A-team" of references, the more likely you are to pick up important details.
• When you interviewed the candidate, you asked him, "What will your last boss say when I call him?" Pay attention to how and whether the candidate's answers diverge from the boss's. That'll give you a sense of how in tune the person is with the ways others see him.
• While you want to figure out any deal-breakers your candidate may not have revealed, avoid sounding like a mistrustful interrogator, fishing for "problem areas," "issues" and "past conflicts." There are more elegant ways to ask this question - like "Can you give an example of a thorny situation he's been in recently, and how he dealt with it?"
• Learn to identify the warning signs that references will give you. That can mean people who do nothing but confirm employment dates, those who damn with faint praise ("He was a pretty consistent worker"), or those who say things like "I wouldn't want to say anything negative" or "I shouldn't really comment on that."

Remember that what you're looking for are the less tangible aspects of a person's performance -- his ability to work well with others, his leadership style, or how well he works under pressure. Positively phrased questions like, "What is his biggest opportunity to improve?" can help get at shakier areas. "Is there anything else I should know when considering him for the job?" will give the reference an open-ended way to alert you to sensitive observations. The more natural the conversation, the more a reference is likely to share information.

You'll find that with great people, you can dig pretty far into their network and have a hard time finding colleagues that didn't like working with them, or who don't have a story about their determination or dependability. It's the opposite with candidates you want to avoid - you may only have to spend 20 minutes on the phone before you start thinking: "Next!"

Update: Thanks to readers for sharing concerns about contacting secondary references. Let me clarify that if you're going to look beyond the list of references the candidate gives you, you need to let him or her know in advance that you'll be doing so. That'll give him an opportunity to tell you which people or places he'd prefer you not contact, and why. If someone refuses to let me talk with anyone but a couple of pre-wired references, I might wonder if there's something deeper going on. And if the person drops out of the running rather than consent to my talking to a few more colleagues, he's likely not a great fit in the first place. Thanks again for reading.

Next up: Hiring Mistake #6: Doing It All By Yourself To see upcoming posts from this series in your LinkedIn news feed, connect to Joel by clicking the "Follow" button at the top right of the page.

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