Drawing faces requires a good understanding of spatial distances as well as proportions.

You may want to check out some videos on how to draw a face from this recent Quora post.

The method of triangulation for faces was developed on the Paintology Drawing app to enhance accuracy of drawing faces.

I have been a traditional artist for sometimes, but have been working int the digital medium for a few years. The digital medium allows you to practice with more versatility than traditional and I have used the platform for many modes of drawing and painting. The aim is to improve and make it easier for artists to obtain the fundamental skills of drawing & painting.

The Paintology Drawing App has been designed around this philosophy and have demonstrated various methods of drawing with good effect including portraits and face drawings.

Face & Portrait Drawings using Triangulation: