You should always make an omelet in a nonstick pan. The best choice for a 2-egg omelet is an 8-inch omelet pan, especially when you're first learning. But any nonstick sauté pan will do as long as it's round with sloped sides and between 6 inches and 10 inches in diameter.

But don't try to make a 3-egg omelet in a smaller pan. Once you've mastered the technique, you can move up to a 3-egg omelet, but you'll want to use a 10-inch omelet pan for that. (Here's a set that includes an 8-inch and a 10-inch pan.) Also, you should always use a heat-resistant silicone spatula, so that it doesn't melt and so that you don't scratch your nonstick pan.