And, after having made omelettes for family members, guests & friends...I'm told that they really ARE good.
Ingredients are pretty simple...use what you want. I do, however use certain things when I make omelettes for guests. We'll ignore the fact that eggs & butter are used, and just list off the "fillings". I don't always use all of these (sometimes I do though)...but other than then cheese, you could choose what you want and add others that might be interesting. The important part is how you cook the eggs themselves.
Cheese - I use Tillamook medium chedder & Tillamook Jack
Bacon - Cooked, and cut into 1/2" pieces
Green Peppers
Mushrooms
Green Onions
Roma Tomatos
Salsa (Mild, but if you like hotter...choose your poison)
*Sausage - Links, chopped
*Ham - Cubed
As I said before, the important part is actually cooking the eggs. Most important is temperature control. My explaination is based on using a gas burner, but you can do it also with electric element...just be aware that using electric means anticipating temperature changes ahead of time.
Crack 3 eggs into a measuring cup or bowl. Whip with fork (or you could use one of those fancy whipping things I suppose...isn't that what those are for?)
Heat a Teflon pan on high or medium-high (one of those with rounded sides...very common these days). Add butter before heatin (I usually use 1/2" of a stick...maybe a little more), and allow to coat bottom of pan, to the point where butter starts bubbling & sizzling a bit...turn down heat to low, wait about 15 seconds and add eggs. Turn burner up a notch or two to medium-low
Eggs will start to solidify on a layer on the bottom of the pan. What you want to do is take the spatula and drag that cooked egg towards the center, and let the liquid part of the egg fill in where you dragged from. Do this from all "sides" of the pan, always dragging towards the center. Over time, you'll end up with a pile of cooked egg towards the center...stop doing this when there's no more runny egg to fill the outside. As soon as egg is not runny, turn burner down to low again.
Add fillings. Do cheese first, and unlike other toppings, spread cheese out over the entire omelette. Remember that the omelette will be folded later, so put the bulk of the cheese on 1/2 of the omelette...but a small portion on the other half won't hurt at all...it melts. Add the other toppings as well, but add them into one side of the omelette.
Turn up the burner again to medium-low and cover. Let the omelette cook for a little while, allowing ingredients to cook as well. Omelette will eventually be firm, and you want to check for the "outside" of the omelette to be lightly browned (check this on the unfilled half of the omelette). Once omelette has reached this stage, fold the omelette...and enjoy