When you're sticking to a grocery budget, paying with cash REALLY helps. Why? When you hand over your hard earned physical money, it just feels more painful! (LOL It really does, though!) It makes you more aware of what you're really spending, as opposed to just grabbing one of many debit or credit cards.
Every week, take out your allotted grocery money in cash, and put it in a grocery money jar just for that use. Put receipts in as your money is depleted, and keep careful track of where the money is going. Once the cash is gone, you need to get creative to use the groceries you already have in new, fun ways!