drink water or tea - take a look at your food budget, how much of it goes to beverages, juice, soda, milk, etc.
always bring a refillable bottle with you - whenever I'm out running errands, I always bring a water bottle with me, sometimes water, sometimes iced tea, but then I'm never tempted by a conveniece store or drive thru. Same goes for snacks if you'll be gone for awhile and especially if you have the kids with you
turn off the car - if your waiting at the drive up, or waiting for the kids, if it's more than 30 seconds, you'll save gas by turning off the car
hang up clothes to dry - the dryer uses quite a bit of electricity, and your clothes will last longer if the avoid the dryer
no school lunches (unless your on the reduced lunch program) - it's much cheaper and healthier to make your own lunches and send them with the kids
buy generic or store brands - we all have the brands that we love, but be willing to try some store brands. I've found that many store brand crackers, juices and dairy products are just as good or better
consider joining a warehouse club like BJ's or Costco - not everything is cheaper and depending on the types of items you eat it may not be benefical for you, but for us we save a ton. Some of the items that we save a lot on - bananas, chips, cheese, salsa, juice, bakery items
books - go to the library or buy used
movies - I bought a lot of vhs tapes for $1 or less, cheaper than renting, especially if the kids watch them 3 or 4 times. I rent dvd's thru redbox, you can also check them out for free at the library