In order to achieve a high degree of likeness in a drawing one must pay attention to what is called the facial triangle. The facial triangle is a term which refers to the brow, cheek bones and the nose. One may notice that this doesn’t necessarily make the perfect triangle due to the shape of the head so it’s better to think of the shape as the image which can be seen below.
Look at the features of the face and see how they are unique. In the image above the features are pretty generic on this woman. Practice drawing and looking at the minute differences that occur in every facial triangle. While the mouth and jawline are also important factors to consider in completing the drawing, the best tactic is to focus first on nailing the facial triangle and then letting the rest fall into place.
So. How does one construct the rest of the face after the facial triangle has been completed? Well the next most important feature is going to be the overall shape of the head. And these head shapes can be comprised into a multitude of categories. Take a look at the gallery below to get a feeling for all of the different shapes that the head can take on.
There are different ways to tackle a portrait with pen and ink, or pencil. The two most popular methods are to either first go for the overall shape of the head, and then fit the facial triangle inside of that shape. Or to first work on the features present, and then add the larger facial shape around them. Neither way is “correct” and it will be up to you to decide which method works best for you.
Caricatures can be a great place to look at the multitude of different features on a face since they are all exaggerated in these drawings and therefore easier to see. When drawing an accurate portrait one will actually use a method similar to those used by caricature artists. And that means that in addition to looking at the facial triangle, and facial shape, that small exaggerations should be made to prominent features in order to make it quite clear “who” a drawing of a person is.