At the telephoto end of the focal range, perspective gets less distorted and slightly flattened. This usually gives a more pleasing and attractive portrait than one that's taken at the wide-angle end of the focal range. Tilt The Camera. Obviously, there are exceptions when you don't want to do this, but very often you can end up with a tighter composition just by tilting the camera and then zooming in. Avoid The Bull's Eye.
Most optical viewfinders have a circle right in the center.
The natural tendency is to place that circle right on the middle of your subject's face. The result is a photo where the lower part of the body is cut off and the upper part of the frame is a mass of wasted space. The use of a simple reflector can make a huge difference in any photograph, but especially a portrait. You can fill in any annoying shadows with some light with a silver or a white reflector. Also, a car windshield reflector works great and is inexpensive.