Cheapest source for Sony Playstation Portable?

Now that the holiday season is fully upon us, it's no surprise that I am starting to receive questions from readers about how to find the cheapest price for specific gadgets. The first that arrived in my mailbox was for the popular Sony Playstation Portable (PSP), and rather than just send along the URL of an online store that was both reputable and inexpensive, it seemed a lot more useful to show how I go through the process of finding the best price online for a given item. If you're going to do even the simplest shopping online, you'll definitely want to read:

    Where to buy a Sony PSP?

This is very much in the vein of "teach someone how to fish, don't give them a fish for supper", but everyone has a different strategy for shopping online. What's your approach?