There are of course a lot of blogs, websites and articles online about how to light a subject properly for stunning portraits. This small article talks about a very simple technique you can use to achieve rich portrait lighting that makes the facial features of your model come to life beautifully. The technique uses only natural light, of the type that comes through your window.
First of all, in most portraits you will want to achieve different levels of light on the face of your photographic subject. This creates some shadows which make the picture look tri-dimensional. If you make your light very even on the face you will make the face of your subject look flat. There is some movement towards even lighting nowadays, especially in fashion and editorial portraits, but you will see that in that case, the volume on the facial features might be achieved with make up or any other means.
If you are shooting with studio lighting, the way you achieve different levels of light is by placing one lamp at a higher power or closer to the subject (this is called the main light) and a second light at lower power or far from the subject (this is called fill light).
If you are new to photography a simpler way to achive this for practicing is to place your subject close to a large window that lets natural light in. Position your subject in a way that the light coming from the window lights part of the face (it can be most of the face actually) and part of the face and body have shadows. Experiment with different angles on your model (relative to the window) and different camera positions. You should expose to the light on the brighter side of your model (that is, expose to the main light). Be careful that the light differential between the illuminated side and the dark side is not too big, because that can create problems. A light differential of 1.5 points is very good between the main light and the fill light, because that creates a 3:1 contrast ratio that looks very good in the resulting image.