I once salvaged a bowl of liquid left after we'd eaten the asparagus at a holiday dinner. My daughter-in-law gave me one of those looks, but I kept it anyway. It makes a rich, delicious and frugal cream soup as does the liquid from other things like potatoes and broccoli.
Another example: I made "half-baked" potatoes - a family "recipe" in which baking potatoes are sliced in two lengthwise, the put face down in a little oil and baked. They're really good, but I digress. ;) Anyway, there were three halves left after dinner. They don't reheat well, like fried potaotes, so I pulled the skin off of them and trimmed off the browned part, grated them, added some salt, pepper and a beaten egg and made very frugal hash brown patties from them. Good eating!
A tablespoon of corn or green beans or peas or whatever... when that's all that's left over, it doesn't seem worth doing anything with. Hold it, though... I don't throw it out. I keep a pint size container in the door of my refrigerator freezer and add the little bits and dollops as they're available. By the time the container is full, I have a good assortment of vegetables for soup or stew - for free. Since I don't eat much soup or stew during hot weather, it gives me a chance to stockpile a little!
Besides things like these, don't throw out radish greens if they're fresh. They're a good cooked green. Salvage large broccoli and cauliflower stems, peel them and eat in a salad or cook as a vegetable.
Got a little leftover rice? Or some chopped raw onions or celery or carrots? How about some leftover hot cereal? Make a frugal meatloaf with it. Add it to ground meat, add seasonings, an egg or two and top with tomato sauce.
The most frugal way to eat is to not throw out anything, but the best way to eat is when you become creative with food.