Try with no flash? In this case, it looks highly unnatural and almost liken to that of a point and shoot.Experiments in portraiture.
Nikon D80
Nikon 70-200mm f/2.8 at ~80mm
Shutter speed - 1/200
Aperture - 2.8
SB-600 flash at -3.0 compensation (aimed at the ceiling)
Also, with any people pictures, be sure to touch up teeth (whiten, smooth) and skin!