Clearly display how many steps there are in total and the prospect's current place in the path. This is a key ingredient to building trust and letting them know that they haven't committed to giving you the next 30 minutes of their life just to pick-out kitty litter. When you ask for your prospect to give you information, give them something in exchange. You'll be much more likely to get what you're looking for this way, and you'll build trust and equality into the relationship. This is especially true in paths built around contests or offers.
Sincerity wins the day Avoid the ad.
Also remember that advertising and selling used cars are competing neck and neck for the low position on America's respectometer. You should know what works and what doesn't by where prospects bail out of the path. Identify problem areas, make adjustments, watch your results and adjust some more. Then once you have your paths selling strong, tweak them to increase the purchase value or push a particular model. And the whole time you're selling you're also learning about your customers, providing excellent sales support and customer service and building solid relationships.