Drop the heat and cover the omlette pan after the bottom has set up somewhat, SG. The trapped steam will help set the top.
Or you can throw it under the broiler to get a drier, 'souffle' effect, as Griff suggested.
I make a lot of eggs.

Three-minute eggs are my favorite for dunking toast soldiers into. Omelets, frittata, fried, scrambled, en casserole, baked in red wine...
Here's a good write up of different stages of boiled egg, and how to achieve each.