Light. That's the main element in every photograph. Break that down and you have two sub elements: highlights and shadows. Control the light - the highlights and shadows - and you have the potential for a cool portrait.
The picture on the left is a natural light image taken with my camera positioned at eye level. The picture on the right was lit with just one light (a light I got at The Home Depot) placed off to camera right. I took the picture while standing on a ladder.
When lighting a subject, remember this: If you want an interesting portrait, don't light the entire subject. Shadows are the soul of the photograph.
I teach lighting on my workshops. Join the fun!