looking at a product you are interested in buying even if it is through a rewards program make sure you take a look at the retailer’s website. Look for their return policy. This is the important part, should you need to return the items, since the actual rewards program cannot take returns.
Inventory: This one is relatively easy to figure out. A store will mark down a bundle of products until they are all sold (or most of them sold) and then mark them back up. This is more common in brick and mortar retail stores than online stores in which you are often dealing directly with the manufacturer. For instance, my stores carry no in-house inventory. We have a deal with our manufacturers who package and drop-ship all items, as do many online retailers, making it a much better place to shop, not to mention more convenient, given the price of gas, traffic jams, long lines in stores, etc.