Pete posts good advice.
Cars are one thing I have not sold, but the art of sales is about the same everywhere.
People are emotional, so good selling appeals to emotion. Zig Ziglar says to sell the sizzle not the steak. Talk about how the customer will feel after making their wise purchase. Also, just about all anyone cares about is the monthly payment.
Tom Hopkins was, I believe, the top car salesperson in the country during his day. He has a lot of good car-specific tips. Basically, he hammered the phones during his down time at the lot instead of standing around smoking cigarettes with the typical average salespeople.
There is a sale made in every interview. Either you sell them the car, or they sell you the idea that they can't afford/don't want it.
Here is a technique taught to me, called 'closing the doors.' Basically, you will always come up against objections, usually price. Before you deal on price, you have to get the customer to admit that they love the product and price is their only objection. They will almost always agree, because the price gives them an easy out. By making them disavow all other objections, it keeps them from jumping over to another excuse after you have come down off the price. You get them to say they would buy, except for the price, and then you lower the price a bit and say, "We agreed that price was the only thing keeping you out of this car, and now we have solved that problem, so lets's get started with the paperwork...."
And like Pete says, it is much like the game with women. It's a numbers game, and the people who can shrug off multiple rejections do the best in the long run.