How to stir fry vegetables

The key to stir-fry is having a very hot pan and very thinly sliced vegetables that will cook on contact. I like to cook my stir-fry in a wok, an Asian frying pan. Woks are great because they give you a large surface area. You can make a stir-fry in a typical skillet, but the problem is that if you pile the vegetables on top of each other they will steam instead of fry.