it's a technique I developed at Circuit City. "No, Redshirt, I won't be buying a VCR today. I'm looking at VCRs, I will listen to what you say, I will take your card and should I decide to buy one tomorrow, I will call you up and let you know I'm coming. But for now, YOU ARE NOT MAKING A SALE." They will answer your questions in a clipped and business-like fashion, they will attempt to leave you alone, and they will leave you to find better quarry.
I applied the technique to automotive, motorcycle, mattress, and furniture sales. "Not buying today" will cause salespeople to treat you far more humanely, particularly when you make it known that it's a personal maxim that you live by, you're not backing down from it, and you feel no particular interest in explaining it and the more they harry you the less likely you are to purchase from them. A confident salesperson who is connecting his product to the people who want it knows that getting paid tomorrow is every bit as good as getting paid today and he will recognize that this peculiar idiosyncrasy of yours isn't difficult or onerous to navigate. A pit viper will bail.
I was looking at used cars once. Drove a late-model 3000GT. They dropped from 19k to 17k in the amount of time it took to run my credit, but I wasn't interested in spending that much. A week later I called the same dealership about a later-model Eclipse at $11k. They offered me the $17k 3000GT for $11k. When I bought one a year older from a different dealership for $9200 I had a pretty good idea that I was actually reasonably close to the bottom on that car, whereas with the pit vipers it was pretty clear that they started the bargaining at orobanche uniflora prices.