I know everybody who's been cooking for a while has probably knows this already, so my apology for boring you. You folks who are just starting out need to know this though.
When you cook a vegetable, broccoli or cauliflower for instance, you trim the vegetable. You'll use the main portion of the vegetable for your main dishes, to keep the cooking consistent, and make the recipe manageable. But 75% of what you don't use in the main recipe can, and should, be saved for later.
With potato leek soup, for instance, you put maybe 60% of the leek into the soup. Now I don't know of any use for the hairy root, so that goes in the trash. But the green part of the leek is perfect, chopped, as a garnish for Peanut Stew, or well chopped and raw, in Couscous Salad, or Taboulli.
And when you cook broccoli or cauliflower, you'll serve the flowery end of the broccoli or cauliflower first. But take the stalk, put it in an airtight refrigerator dish, and save it for a few days. When you need a quick meal, take the stalk, peel it lightly (remove the outer edge, the toughest knots where the various branches split from the stalk, and cut off the end which may have gotten a bit tough from the air), and slice it crossways into 1/4" thick medallions. A little lemon juice, cumin, and / or garlic makes that pretty good, microwaved til tender. Or put the slices into Peanut Stew.
Those of you with crock pots probably put everything into a stew, on principle. OK, my apologies for boring you here. The rest of us can learn other tricks though.