1. Jacques Pépin once said that in his kitchen, he always had an empty milk carton at hand, and into it would go all the bits of meat and vegetable trimmings—peelings and tough stems and end pieces; then he'd put it in the freezer. When it was full and he wanted to make a soup or stock, he'd pull out the carton, slash it open, and dump all those discards into the soup pot. Not a bad idea, particularly in these days of soaring food prices.
2. Buying bread can be a problem for the single cook because seldom does one encounter small loaves. But bread freezes well, so what I usually do is buy a baguette or some other crusty loaf, and what I don't eat the first day I'll cut into four or five pieces, wrap separately in foil, put in a freezer bag, and freeze. I'll pull one out in the morning so it's ready for supper, heated up a touch. You can do the same with any kind of bread.
3. Don't throw away those few tablespoons of cooked spinach, or the three of four extra spears of asparagus you couldn't quite finish; they can be used in a soup, a salad, an omelet, or a frittata. The little bit of precious meat juice left in the pan is worth saving to use later to intensify a soup or to make a pan sauce.
4. Pour extra stock or broth into an ice tray and freeze. When frozen solid, remove the cubes of stock and put them in small freezer bags. This way you can easily retrieve a few cubes when you need a small amount to make a pan sauce or to thin and flavor a sauce or soup.
5. Fresh herbs can be a problem for the cook living alone—or, for that matter, for any cook today. So many recipes call for two or three different ones, which are expensive, and you're apt to throw out the limp remains. One solution is to substitute dried herbs, which good cooks have been doing for ages. Start with about one-quarter as much dried herbs as you would fresh, and taste. Another strategy is to grow a few fresh herbs in pots on a sunny windowsill, if you have one.
6. When you've bought more mushrooms than you can use up, a simple way to keep them is to dice and sauté them. You can then pack the sautéed dice, which the French call duxelles, in a small freezer bag and dip into it whenever you want a tablespoon or so to add to a sauce, a soup, an omelet, whatever.
7. It is very convenient when you are roasting a chicken or a piece of meat to roast at the same time a pan of different vegetables—beets, fennel, leeks, parsnips, peppers, squash, tomatoes—so you can have them on hand for salads, or to be mixed with pasta, grains, rice, or eggs.