Each portrait must exemplify a trait or characteristic that is unique to your subject. Your aim should be to make your viewers learn something about your subject, which can be done through both character and environmental portraits.
For character portraits, if at all possible, photograph your subject when he or she is unaware, when they are most comfortable and relaxed (or at least, without the burden of knowing someone is photographing them). The subject should most of the frame – all focus should be on your subject. Try to make the atmosphere of your shooting space comparable to the mood you want your subject to reveal. For example, if you are aiming for serious portraits, talk about serious subjects to set the mood. Get to know your subject so you both can make the most out of the experience. To really focus on what your’e doing, use simple lighting (such as natural light from a window) so you aren’t bogged down with complex, time consuming exposure readings. If possible, use a hand held remote so you aren’t obliged to even stand behind the camera.
Environmental portraits reveal even more about your subject than character portraits. They are also much more effective for making your subject feel at ease during shooting. For example, if your subject is an avid cello player, try photographing them in the studio or practice room, when they can be completely absorbed in their work and forget about the camera. This allows you more time to take more complex exposure readings while your subject is distracted. Environmental portraits can tell stories about your subject your viewers may not have otherwise known about. Use a deep depth-of-field to ensure all aspects of your photo are in focus.
The most important part of portraiture, regardless of the type, is to make your subject comfortable so that you can best capture their personality. Maintain open communication with your subject, and if something makes them uncomfortable, remedy the situation or if it cannot be fixed, do not bother them with it.