Few things to remember:

-Perception means everything, what the customer perceives as a deal doesn't necessarily have to be a deal at all. You can make both the management and the cusomter happy.

-You've got to make the customer feel at ease, feel free to get on a personal level with them so they feel comfortable. Get to know their kids, family, and their situation. Become their friend with a huge smile and be very courteous. Act as if you genuinely care about their needs and wants.

-Make it seem that your on their side of the deal and that your busting your ass to get them the best possibly deal they can and that the unknown manager is the evil one.

-Nothing beats experience, give it time and you will learn and excel.