Photographing people is one of those things that most photographers either shy away from or completely incomplete. Personally I tend to shy away from it. Lately, however I took a few candid shots on black and white film and have been delving a little bit into into portraits shots. In this article I've outlined what I've learned to make a good portrait photograph.
Find a setting that works. One of the main criteria that seems to separate my good portraits from the poor ones is the background / setting. You want to achieve one of two goals: Option one is to choose a setting that completely compliments the subject (for example, a mechanic in an auto shop or a person at home). Alternatively, option two is to choose a setting that puts your subject so out of place that it spikes curiosity (such as a man in a suit standing on a country road, or a child dressed in a suit and tie at a country club). These create images that challenge stereotypes and give your viewer a reason to look at and think about your image. Usually I choose one of these two extremes as something in the middle often turns out fairly underwhelming. Images in between usually neither achieve the synergy of a picture where the person matches their surroundings nor the intrigue of an image whose subject is in an 'out-of-the-norm' setting.
Keep the eyes in focus. This was something that I had heard since my first photography classes years ago but never realized the significance of until I dabbled in portrait photography myself. Keeping the eyes of your subject in focus and clear help to create a strong connection between the viewer and the subject of the photo. Our eyes seem to give away our every emotion, and this is harshly evident in photography.
Now I'm not saying that you can not take interesting pictures with your subject looking away, nor that you can not come up with your own unique settings that do not lean toward either of the extremes I talked about earlier. These are simply my experiences and what has produced the images with the most impact for me. Just remember to be creative, good luck!