Long queues: Nobody wants to wait hours just falling in line at the cashier! Especially if you aren't carrying that many items in the first place, and had wanted to just come and go. Some insensitive customers, however, take too long on transactions: putting an item back in the shelf, forgetting an onion, using coupons for every item, harrassing the lady at the cash register, or counting change at an unbelievably leisurely pace. That's why if a store has an express check out counter - for those with baskets only, and not carts - then that's where I would fall in line.
Take advantage of your current grocery store or drug store loyalty cards. Giant Eagle, for example, offers Fuel Perks