Everybody who wants to be great at sales needs to master one skill: the art of listening. The better you become at listening, the more you sell.
But don't be the passive listener whom the prospect uses like a psychotherapist - babbling on about whatever he wants to get off his chest. Great salespeople actively direct the course of a conversation by asking astute questions.
This sounds great in theory - but try putting it into practice, and you'll see how hard it is. Prospects quickly become uncooperative, antagonistic or flat out tell you that they don't want to answer your questions.