Always ask for a raincheck if an advertised special is out of stock. While you are waiting for the product to come back in, look for more coupons for that product or order them online.
I can't begin to tell you how much money I've saved by doing this! I love doing this at CVS especially when they are out of a product that is *HOT* that week. I usually go 1 or 2 weeks later and still get the great bargain!