Portrait is defined as, "A likeness of a person, especially one showing the face, that is created by a painter or photographer, for example." In the area of portrait photography there are some guidelines that you should consider when you go to take photos of people.
The different types of portraits are: close-ups, facial shots, upper body shots or environmental portraits. Environmental portraits are where you focus on the subject and on their surroundings that provide more character to the subject.
When people have a camera in their face it usually makes them nervous and they will try to put on a face that does not portray who they really are. The real skill to portrait photography is trying to capture photos when the subjects are comfortable and not worried about a camera.
Many professional photographers try to capture their subject's true essence by using tricks. One example of this is counting to three so the subject prepares and then while they are relaxing after taking a planned photo the photographer will snap a few more unplanned photos. In most cases the subject won't even know that more than one photo was taken but it's usually the photos that the subject wasn't expecting that capture their true essence.
Another more common strategy professionals use is to tell funny jokes that make their subjects genuinely laugh or smile. I'm sure that you have probably experienced something like this yourself.
These usually have the subject's shoulders and head or less. They are framed around the face. These are the most common and best at capturing expressions and glamour shots. For these it is very important to have the light coming from a good angle. To accent wrinkles or small details you should have the light coming from the side or from the top. To create flattering pictures you should choose a cloudy day or try to create diffused light so there are hardly any shadows. Also make sure the subject is brighter than the background to reduce distraction.
For close-up portraits you should use a wide aperture (low f/stop) to make the background out of focus and therefore less of a distraction. Professionals commonly use a fixed telephoto lens that's 90 mm or higher for portraits in order to de-emphasize the subject's nose or any other unflattering feature. It works because at that distance the nose or any other feature does not seem closer to the camera than the rest of the face.
UPPER BODY OR MIDRANGE PORTRAITS
These are easier to capture because the subject is probably more relaxed because it's less personal. These include a little more of the background than close-ups. These are commonly used for both single subjects and multiple subjects. This is the kind of portrait used to mark occasions such as graduation, yearbook, birthdays and other parties. The ideal lens would be about a 90 mm fixed telephoto or more wide angle depending on how many subjects there are.
These are the portraits that let you into the life of a subject. They might include the whole subject in a scenario or the subject participating in some hobby that they enjoy. These are best for telling a story to the viewer about the subject. They are almost always used by photojournalists to look into the lives of interesting people. They also make great Black and White pictures.
Use this information to develop what kind of portrait style you would like to take, and then practice it before dealing with any serious clients.
Richard Schneider is a digital photography enthusiast and founder of http://www.picturecorrect.com/ which offers tips and news about digital photography, digital camera reviews, photoshop tutorials and computer wallpaper.