The biggest mistake an interviewer can make is to accept generalities (“My boss says I could communicate better”). The solution is to probe for specific examples so you can accurately rate the candidate on that competency (communications in this case).
Without probing for specifics, you may assume that the problem is serious (violates confidences, fails to alert the boss to problems, publicly berates team members) and end up hiring a C Player. On the other hand, you could assume that “everyone has potential to communicate better”, and fail to probe enough. This could potentially result in not hiring an A Player, whose communication problem is minor (an occasional typo, very good speech maker but could be even better).
Here’s an example of how to fix “accepting generalities”, such as communication skills:
C(andidate): My boss criticized my communications skills.
Y(ou): How exactly did she want you to communicate better? (Re-ask the question)
C: It was my communications with my peers.
Y: In what specific ways did your boss want you to communicate better with peers? (Ask for specifics)
C: I guess I tend to be a little direct at times.
Y: Like what times? (Ask again for specifics)
C: Ok, I’m so passionate I lose my temper quite a bit
Y: If we had a video of your losing your temper recently, describe what we’d see. (Can be revealing)
C: Just last week I didn’t like Joe’s conclusion and I stood up and called him an idiot.
Y: How would your boss rate your peer relations overall? (Nail down how serious it is)
C: Mediocre I guess. (It’s serious!)
US News & World Report published, “10 Mistakes Job Interviewers Make” and “Not probing deeply enough”, was at the top of their list The other 9 pitfalls are rookie mistakes – mis-treating candidates, not knowing what the job is, etc. Keep probing until you can rate the candidate, and you’ll hire better!