Find a location with good light for a portrait shot. Place your subject some distance in front of a simple background and select a wide aperture together with a moderately long focal length. Take a viewpoint about one and a half metres from your subject, allowing you to compose a headshot comfortably within the frame. Focus on the eyes and take the shot.
The background blur created by the shallow depth of field makes the subject stand out really well. The long focal length (100mm) slightly compresses the features in a flattering way, so is ideal for portrait photography.