One of my favorite questions is one that I ask towards the end of an interview. “If I went to go to your last place of employment (I usually name the company) and talked to someone you worked closely with, what would they tell me about you?”
When the interviewee answers, it is amazing how other things come up. Often they start out by answering, “Well they might say this”—and then the interviewee gets going and very quickly you find out a lot more about the person in front of you.
