Whisk eggs or egg whites with salt, pepper and seasonings. Sauté any omlet fillings you'd like (chopped onions, peppers, spinach, and so on), then pour the eggs over the vegetables, evenly distributing them in the pan. Alternatively, if you're after, say, a bacon and cheese omelet, cook the eggs first, then sprinkle your filling in the middle.
After about 4 minutes, your eggs should be cooked. Sprinkle in cheese as desired, fold and serve.
See recipe: Cheddar and Spinach Omelet
Want to see the technique in action? Watch this video on how to make the perfect French omelet.