If you've ever bought groceries, you've looked at a sale paper. Before you went to the store, you checked to see if anything you needed would be cheaper that week or perhaps on sale at a different store entirely. Some things you only buy when they are on sale, and so you carefully scan all the circulars to see if this is the week you can get everything you want to fill the pantry.
Sale papers (and coupons, for that matter) are some of my best friends. With that said, problems can arise when we treat church with the same mentality we treat Kroger. "Church shopping" is a phrase of relatively recent origin, and it refers to the way Christians now visit multiple churches before deciding to regularly attend one. It can also denote the appraisals made by the "shoppers" themselves: feelings about music, the sermon, the people, the building, the programs, etc.
On the one hand, it behooves us to make sure we're called to join a particular congregation. On the other hand, church shopping emphasizes all the wrong things. It treats worship as a product to be purchased and consumed instead of an act of devotion to a loving God. It makes it all about us -- what we want, how it makes us feel. Church isn't about us, though. It's about God. We worship God because of who He is, not because of the really excellent praise band or anything else we ourselves do. If we consistently fail to realize this truth, if we always get nothing out of the service, maybe it's because we're not putting anything into the service ourselves. Maybe it's because we're consuming, not worshiping.
Use your grocery sale papers, but stop treating praising Jesus like a supermarket. Get connected, get committed, and worship the One who saves souls.