No, I don't mean you should eat Mac and Cheese or Ramen for every meal. Or for any meal, for that matter. But if you're like me, you can easily get caught up in trying new foods, or using a lot of expensive ingredients in your food. Even if it's only for a few meals a week, those add up fast. Instead, go back to the basics. A friend of mine told me that if you want to eat frugally, think like a peasant. Soups, for example, are quite cheap and can make a ton. Make a big batch, keep a few servings out to eat, then freeze the rest to pull out for an easy meal later. (Having meals in the freezer is a great way to stretch a future dollar when money is even more tight than it is now.)
Don't shop for convenience. Instead of buying boneless, skinless chicken breasts for $2/lb (or less if you're watching for deals), buy a whole chicken for $1/lb. (These go on sale quite frequently.) You can roast a whole chicken, eat it in various ways for 2-3 meals (chicken breasts for one, fried legs or wings for another, shredded chicken in enchiladas for another), then use the leftover bones to make a chicken soup, or chicken stock for another meal. And that soup can last for several meals. Besides, cooking chicken with the bones and skin on will keep it more moist and more flavorful. (If you don't want to eat the skin, that's fine. Just pull it off after it's cooked.)
Eat more produce. Not only is it healthier, but it's cheaper than buying processed foods. It can also keep you from snacking on unhealthy foods throughout the day. Trust me. A bag of carrot sticks is much cheaper than a box of Ding Dongs. And you get more. A quick salad is a cheap and healthy side dish for any meal. (A head of romaine lettuce for $0.88, a bag of carrots for $1 or less, and a couple of tomatoes for less than $1, makes enough salad for several servings. Just go light on the dressing if you're doing it for health reasons.)
Rotate through your top 7-14 favorite meals. It's ok to have some repetition in life. You don't need to make a new dish for every night in the month. Make a shopping list for each meal, then when you see things on that list go on sale, stock up. This is especially helpful if your favorite meals use similar ingredients. So when you find hamburger on sale, you can stock up for chili, stroganoff, and Shepherd's Pie.
Do some vegetarian meals. Pasta, veggies and a simple sauce can be a good, filling meal. Especially if you have side dishes. Salad, vegetables, fruit, bread, can all make a less-filling main dish into a well-rounded, satisfying meal. Meat can be expensive. So if you can cut meat out of your diet for a few nights every week, you'll save a lot of money in the long run. (This is a hard one for me. Born and raised on a cattle ranch, when I plan dinner I typically pick a meat and build a meal around it. Take out the meat and, well, what's left? I'm getting better, though.)