Because everyone's appetite is unique, I can't tell you what portion sizes are right for you. But here are some starting points:
ProteinPortion sizes for meat and fish can vary substantially, depending not only on your appetite, but also how the protein is served, what other dishes accompany it, how rich it is, and whether it contains bones. A four-ounce piece of cod or probably won't be enough for most people - unless it's deep fried or accompanied by something rich like risotto. But a four-ounce Italian sausage is pretty filling, so it will probably constitute a serving.
Sometimes you'll luck out with precut pieces of meat, but don't always assume that a single chop or steak is one serving - a thick steak can weigh more than a pound, and could be as much as three or four servings for some people.
GrainsMost grains (rice, bulgur wheat, barley, grits) expand upon cooking to about four times their dry volume. Thus, 1/4 cup (four tablespoons) of dry rice will give you about one cup cooked. This might be one serving, or two, depending on what else you're having, your appetite and other factors. Because they expand so much, it can be difficult to cook small servings of some grains. I've cooked as little as three tablespoons of rice or grits, but you do need a very small saucepan for this amount.
PastaTwo to three ounces of pasta (dry) is probably the portion range for most people. (Restaurant portions of pasta are often five or six ounces - they're huge because pasta is cheap. If you like those portion sizes, by all means cook them!) For most people, though, I recommend starting with two ounces per portion for dishes with lots of other ingredients (meat, vegetables, rich sauces) and three for dishes where the pasta is the focus. For two ounces of pasta, 1/4 to 1/2 cup of sauce will probably be the right amount.
VegetablesWhen determining portion sizes for vegetables, one thing to remember is how they can change upon cooking. If you cut up a couple of carrots and steam them, the cooked portion will be about the same volume as the raw portion. But if you roast them, they'll shrink considerably because of water loss. With spinach, the difference is even more dramatic. That 10-ounce bag of spinach might be four portions if you're using it raw -- in a salad, for instance. But cooked, it will collapse into less than a cup - that may be two servings, or even just one.
A Few Tips to Get Started
- You probably already own measuring cups and spoons, but this process is much easier if you also have a food scale. If you try to guess with things like pasta or meat, chances are you'll cook too little or too much.
- To begin with, you may want to take notes on recipes as you make them -- that way you won't have to rely on your memory. As you get more practice, you won't always have to do this, but it helps when you're just starting out.
- Don't worry if you make mistakes -- if you cook too much food, you can often freeze it or use it later. Here's some advice on dealing with leftovers.