Yesterday I visited a friend at his office. I stopped and asked the security person near the elevator what floor his office was on. When I mentioned my friend's name, the attendant said, "He's a nice guy."
I've been thinking about his comment ever since: He's a nice guy. My friend had made a good impression on someone whom he had no reason to try to impress.
My observation is that the way a person treats folks they do not have to try to impress - waitresses, custodians, security people, and the like - says a lot about them. If you are kind to people you don't have to impress in order to get along in life, you are a nice person. If you are unkind to these people, you are not a nice person.