Another thing I've found is that places like Costco and Sams are not always the cheapest alternative. It may be convenient to pick up certain items in bulk. But I never buy anything that is a name brand so that lets out most canned goods, condiments, and treats. And I won't be sucked into the ready-to-microwave dinners for $8 a piece.
Costco has good deals on milk ($137/gal), I've compared the cost on the big bale of toilet paper and it is cheaper than the mid-line grocery store stuff, same with paper towels. Foster Farms chickens for 99 cents per pound is a bargain here. But their meat is way out of line.
We don't buy soda...Kool-ade, tea, tap water is far cheaper. I don't buy chips, cookies, snacks. If the kids want cookies they have to be industrious enough to bake them. We don't ever eat out. The only "fast food" meal we get is a huge pizza from the Costco cafe on the one day / month that I Costco shop.
No matter where you shop, take a list and stick to it. Ice cream can be a treat around here at the end of the month...IF there's any money left over in the grocery envelope...which means they've scrimped a bit during the month.
That's another thing that has saved my bacon with budgeting...every month we sit down to do bills around the 20th since that's when hubby gets payed...once per month. All of the utilities, mortgage, insrance is on a monthly pay plan where they automatically deduct from our checking. So that is already built into the budget (our utility companies will divide your total yearly useage into 12 equal payments so no ups and downs during the year). Then we have envelopes for allowance, groceries, gas. The budgeted amount goes in there and everyone is responsible for their own gas useage, allowance expenses...I take care of most of the groceries. Envelope is empty? You're done for the month.