Ben Stein writes well about the Art of Selling, and a good salesperson truly practices art:

In other words, align your interests with those of the buyer. Don’t try to shove something down his throat. Don’t try to hoodwink him. Just listen to what he needs and wants, see if you have the good or service he needs and wants and then arrange to make it easy to buy. Make sure that the buyer is a real buyer with a real need, a real timetable to buy and the real means to buy. Then satisfy that need.
It is also important to be a friend to your buyer. In fact, I observe that almost all success in life comes down to being a friend to someone: a friend to the voter, a friend to the judge, a friend to your spouse, a friend to the client, a friend to your parents. As Miller said so aptly, you have to not just be liked, but “well liked.”