If you've ever made homemade whipped cream, it's the same process. But if you haven't, I promise it's not hard to tell. When you detach and pick up the whisk beater from the mixer, and turn it upside down, so the whisk end is facing up, the egg whites will stand up in a peak (like a little mountain), and not fold over onto itself. This is a great visual guide from Taste of Home.