Non-stick woks work best for cooking omelettes. Gently work your spatula under the omelette and gently wiggle it to release the omelette from the bottom of the pan. Keep working it underneath until the bulk of the weight is held by your spatula. Lift just high enough so the edges won't fold over themselves then and quickly turn your wrist to flip it. Another option is to gently slide the omelette out of the wok onto a large plate. Flip the omelette over to its other side and then slide it back in.