SNACK before you go. Heck, you can even bring a snack bag of nuts into the store to eat while you shop!
ADAPT your menu plan to whatever is on sale...if you don't mind flying by the seat of your pants once in a while!
SIZE check! Some pricing is tricky, especially at Walmart, where they sometimes make the smaller quantities less expensive per ounce!
STOCK UP with non-perishables when they go on sale and at whatever store is the best price!
YANK packaged products from your cart for the sake of YOUR HEALTH and YOUR WALLET! Reasonably limit yourself to fewer packaged products -- a bit less than usual. Rather than just saying "a bit less", spell it out. For example, if you buy two boxes of cookies per week, then try buying one box per week.