From StoryEvent:

[First,] you indicate that you’re interested in buying a big fat warranty…

…then ask ask the sales assistant to lower the item’s price. Since big box electronics stores are often pushed to sell warranties, they’ll be willing to budge on the price of your item - especially if it’s got a big price tag.

[But wait, there’s more…]

Then when checkout time comes, you have a change of heart on the warranty. Simple enough.

(HT to Lifehacker)