The secret to good portrait photography is getting to know your subject. Portrait photography isn’t about lighting a human head properly, getting that person to smile and then saying cheese while at the same time taking the picture.
We are all used to the above mentioned style of photography from our school days. A photographer would come in, sit us down, position us, work behind the camera for a bit and flash. It's over.
However, this by no means is portrait photography. The purpose of portrait photography is to draw someone's personality out. A good portrait photographer will be able to show the friends and family of their subject the pictures they took and the response should be "oh my, that is very much like Harry" or "that is his famous hand gesture and facial expression". A portrait is about getting to know a character and then catching them in their moment. As a photographer it's very challenging to get to know someone in such a short period of time. You'll have to ask the right questions (without prying), study your subject (without being obvious) and have the camera ready at all times in case one of these magic moments happen to pop up.
Your goal is to capture a person's physical likeness on film. You will do this by using the proper equipment, but will also try to capture their expressions and body language. A character does not need to smile for a portrait to be successful. Sometimes a thoughtful look will be more representational of the look of your subject.
photo by sukanto_debnath
Other photography articles of interest:
How to read a photographs histogram
Advanced photography tonal range
Different types of photography
Different types of landscape photography
How to take landscape photographs