You have to listen to a persons wants and needs, not just blather on about "the latest and greatest", for one. It's not as simple as answering questions. Some people don't even know what answers to ask. That's your job to determine needs and wants.
Secondly, you have to meet certain goals, and have a "way" with people. Hopefully not the way of the usual salesman who knows nothing, doesn't listen and thinks he knows it all, including what the customer needs, even if the customer knows that full well.
What's worse is salesmen who gets offended when their sales pitch doesn't work because the customer are well-informed beforehand. Or are spewing regular nonsense and hear-say in order to sway a customer, even though the salesman has no experience whatsoever, except an experience in putting forth said sales pitch.
Of course, those are not the entire story, but retail is certainly not for anyone. Well, "sale" in general is not for everyone.