What is the most important thing in sales?

I went to interview on wednesday for an IT selling position. The interviewer asked me what are the important things in a salesman. I answered him the things that David Jones had taught me, things like: building relationship, be friendly and stuffs like that..

Apparenlty my answer wasn’t the one that he’s after, he still asked the same question for few times, I felt bad already.. He finally said, the most important thing is listening to customer’s needs.

Of course, that’s very obvious, it just didn’t occur to me at that point of time, or maybe I did imply that by building good relationship with the customer. But I reckon diferrent people have different opinion on that matter..