Taken from http://www.how-to-draw-and-paint.com/how-to-draw-faces.html
Remember, practice is everything when learning how to draw faces. Copy examples from photos, newspapers and magazines or of course, you can use the examples in this tutorial.
Get as wide a range of sketches as you can of men, women, young adults, the elderly, children, racial and ethnic backgrounds and so on.
Draw faces from as many different angles and lighting conditions as possible. It's surprising how the same face can look quite different in contrasting lighting conditions.
However, one step at a time. Let's get used to drawing a 'general' face that has all the relevant bits in the right place!
Oh yes. And one other point.
The 'standard measurements' I've just mentioned are only a guideline, not an absolutely rigid formula that must be adhered to. So use them as a valuable tool. Don't become a slave to them!
How to Draw Faces - Stage 1
All we start with is a basic oval in Sketch A. Draw this in lightly and don't worry if it's not perfectly symmetrical.
Few people have a head shape or features that are identical on both sides of their face.
And here's the first standard measurement - I'll call these SM from now on to save space.
The centre of the eyes are placed halfway down the oval - not about a third of the way as you may think. Also, the ears are attached to the head on line with the eyes.
The bottom half of the oval can now be split in two again to fix the position of the tip of the nose. The remaining space below this is also divided in two and the imaginary line here positions the mouth.
Even though Sketch B shows this with the eyes & ears, nose and mouth only very simply defined, you can see how everything 'looks right' already