Ami asked for an explanation of complete proteins, so here's the "quickie" answer; keep in mind this really over-simplifies it (which sounds funny since my post runs on so long), but it's enough information for practical use.
To "build" protein, there are a number of amino acids necessary (called the essential amino acids by some writers). Some your body can produce from other nutrients, some it can't, but if it doesn't have all of them, it can't produce the protein that your body needs. And it has to get all of the ones it can't produce at about the same time, within about an hour I believe.
Meat, eggs, milk, soy and most nuts are complete proteins, that is, their protein includes all of the essential amino acids your body can't produce. If a meal includes a serving of one of these, you can probably use all the protein in the meal. There are other foods whose proteins include some but not all of these essential amino acids. These include grains---corn, wheat, rice, barley, millet, and oats--- and legumes---peanuts, beans, peas, and lentils. These are incomplete proteins. However, the protein in the grains mostly lack the amino acids that the legumes have and vice versa, and they can "complete" each other.
That means if you eat a slice of whole wheat bread (a grain) with peanut butter (a legume), you've given your body all the amino acids at one time. Beans and brown rice or split pea soup with whole wheat bread or corn tortilla with black beans are other examples of combinations. And if you have an incomplete protein with a complete protein, you're fine too. I can't recall right now where sunflower and pumpkin seeds fall, complete or incomplete, and there are a few others.
This probably sounds complicated. But it's really a lot simpler. If you have food from at least two protein groups (meat, dairy, nuts, seeds, grains, and legumes) at a meal, you should have a complete protein. Drink a glass of milk or soy milk with every meal, and you won't need to think much about this.
Just a note: there are a very few research studies that suggest your body might store the incomplete proteins for later combination, but I believe a lot of other research contradicts that. Probably safer to go with the more conservative one hour figure (and I aim to get them at the same time when possible).