Food: Read up on extreme couponing.
Also, whenever you buy anything, check the receipt to be sure it's correct. Some groceries will give you the item for free if they overrang it. (Some won't, but at least they'll give back the amount the overcharged.)
Shop the sales, check the unit price before deciding which size to buy (sometimes the "large economy size" actually costs more per ounce or whatever than the smaller size), shop in the mornings for meat, as yesterday's meat is often discounted first thing next day but may sell out by afternoon.
Switch over to the fluorescent lightbulbs.
Drive within the speed limit as it uses less gas. Keep your gas tank full and your oil changed for more efficient car engine function.
Swap and barter where you can.
Try starting a garden, even if it's just some tomatoes in a pot.
Call the utility companies to ask what kinds of budget plans they offer.