Food is usually a substantial part of a household's budget. Fortunately, there's also lots of opportunity for saving money on food.
The big budget-killer is usually dining out, so reducing the eating out to a minimum is low-hanging fruit. Beyond that, it's a matter of spending time to get good deals on food and preparing meals.
Preparing food means, among other things, foregoing individually-packaged items and going for items that need to be divided up. Individual packaging is convenient, but it's also more expensive because there's extra cost that comes with the extra processing and packaging. Take, for example, K-Cups, or pretty much any 100-calorie size.
It does take time to prepare servings, and time isn't free, but with some things the food does taste better than it would if it were bought prepared. Take cubed cheese, for instance. The cheese that comes on a prepared tray is likely going to be more dried out after it's been sitting around in the refrigerated section of the grocery store, than a block of cheese that was cut up right before it was served. Why? All of the extra surface area exposed to the air makes it dry out faster.
Geeky aside: It's easy to cut a pound of cheese into pretty accurate one-ounce servings for counting calories if you're trying to lose weight. Cut it in half lengthwise (2 pieces), cut it in half crosswise (4 pieces), halve each one crosswise again (8 pieces) and again (16 pieces).
We've found that reusable plastic containers (like Glad or Ziploc brand) are our friends. They keep things fresh nicely — especially cheese and veggies. I'll take a head of cauliflower and break it up (takes about 5 minutes) into a few pint-sized plastic containers. This lasts me a day or two at work and satisfies the munchy-crunchies.
One last thing: It's usually the case that unprepared, un-divided-up food is cheaper than an equivalent amount of portioned food, but not always. The best deal we've found on broccoli was a bag of bite-sized florets at Costco. It's a fairly large bag, but it's the same price as about half of that amount in a single stalk in the grocery store.