Buy Ingredients, Not meals

Swim the perimeter of the supermarket.  Try not to go down the aisles.  You pay dearly for the convenience of convenience foods.  Buy the ingredients for your meals.  Stay away from the expensive prepared stuff that is high in preservatives and low on nutrition.  If you want your meals prepared for you, go to a restaurant.  At least there you won't be fooled about over paying.  But for saving money there is nothing like making it yourself.  If you make your food from scratch, you know what's in it.  If you buy prepared food, you must read the labels diligently.  It's shocking the kind of crap that ends up in a jar or can.  Personally I prefer frozen veggies to canned.  I find them to be fresher and cleaner than canned or jarred stuff.  Don't go down the aisle except for cereal maybe.  Lately I have even been making my own cereal.  I find the store bought granola is too sweet for my taste so I stretch it with raw oatmeal and add extra nuts and seeds.  Less cost, Better nutrition and it keeps you full longer too.
On the other hand, it's better to pay for quality.  I have discovered Greek yogurt.  I buy a tub of the plain and sweeten it myself with preserves, pure vanilla or syrup.  It costs a little more but it's worth it, much  better quality.