Blanching is a very common technique for preparing vegetables, but you can use it for meat, as well. It doesn’t involve much more than popping your food into boiling water for a minute or two, and then (usually) putting it immediately in cold, or iced water, to stop the cooking process.
Cooking many vegetables briefly in hot water makes them tender. It can brighten their color quite a lot (carrots, broccoli); sweeten them and cut a harsh taste (bamboo shoots, onions, bean sprouts); or just leave them tender, but not mushy (mushrooms, asparagus). To blanch vegetables, cut them into the size you want. Try to keep the sizes pretty consistent, since it will affect cooking time. Smaller pieces cook faster.
Have a bowl of iced water ready. It will need to be big enough to submerge all of your veggies.
You’ll probably want to blanch one kind of vegetable at a time, if you’re doing more than several kinds of vegetables. They will all take different amounts of time. Plunge them into boiling water over high heat. The water should start boiling again in less than a minute (if it doesn’t, you’ve put too many veggies in at one time). As a rule of thumb, you probably want about twice as much water, by volume, as your vegetables.
Test for doneness after about 30 seconds or so (pull a piece out, rinse it in cold water, and taste). You want it to be brightly colored, and starting to turn tender, but still crisp (not soft).
Drain the vegetables. Don’t burn yourself. Remember, if you save the water you can reuse it, for multiple batches. Immediately dump the hot veggies into the ice water. When they’re cool, drain them, and use them.
Blanching meat is common in Asian cooking, when making soups, braises, or stocks. When you first start boiling raw meat or bones, you can get a dirty looking, scummy foam that forms on the surface of the broth. This is not actually, dirty, and it doesn’t taste bad, or hurt the food. But, you can get a more transparent, nice looking broth if you blanch the meat first.
Don’t do this if you’ve browned the meat first. This will totally defeat the purpose. With browning, you want to collect as much of the dark brown bits. They have the umami you’re trying to capture. Blanching would just wash these away.
The general technique for blanching, then, is to put your raw bones or meat into cold water. Bring it to a boil over high heat. You’ll probably see the scum start to form as soon as the meat starts to boil. Take it off the heat, rinse it in cold water, and then use it in your recipe.