We go to Costco about once every eight weeks or so.  Surviving any trip to a store these days requires some sort of bribe for Melody to keep her quiet throughout our visit.  Typically I bribe her with puffs or some other snack along with water.  On occasion, I will bring her a toy of some sort to keep her entertained.  However, Costco can be a much longer trip than our average grocery run.  We spend at least two hours a visit most of the time.  We walk up and down every aisle to see what's new and what we think we need [we always walk out with at least one thing we didn't plan to buy].