Kudos to @dotknott
for mentioning the bar code scanning capabilities of the Wal-Mart iPhone app in the clearance thread:http://www.bricksetforum.com/discussion/4903/us-walmart-clearance-30-50-off-hp-potc-some-star-wars
Here's a quick guide to using it to find potential deals in your area. With this guide you'll be able to find out if sets are marked down at a particular store, without having to physically visit the store. There are then additional steps required to figure out if the store has the item in stock (or at least according to their on-line inventory system).
Step 1 - From within the Wal-Mart iPhone app, choose the "Stores" button and find a store to search. Click the blue arrow button to choose the store.
Step 2 - With the store now selected, choose the "In Store Now?" button. This is usually the "Forget what my stinking iPhone GPS is telling you, I'm *IN YOUR STORE*!" button. You can conveniently press this when sitting on your couch at home.
Step 3 - Now that the app thinks you are in the store, you can press the Scan button as if you're going to scan some product on the shelves.
Step 4 - Grab one of the 50 QARs from your shelves (if you have a ten gallon hat), use your handy dandy graphite colored bar code cheat sheets, or navigate to the most useful site on the internet (Brickset) and find the product page to get the barcode on your computer screen, and scan away.
Step 5 - Let the mashup of Sam Walton's, Steve Jobs', and Al Gore's labor inform you if that store has a price you agree with.