How I sketched it - 1
Step by Step sketching lesson from a student

Original Picture. It is the actual size of the image. I tried to scale it nearly 4 times of this one. If you notice this picture is too small and has too much of light on the face. Too much of light kills the shadows. That's why flash camera images won't be able to capture the structure as is.
This picture gives lots of opportunity for the artist to assume and creatively fill the gaps where there are no details.
Artistic exaggeration makes the picture more clearer and appealing. It won't look nice if the low detailed areas are mimicked as is the original one. It is better to assume and sketch the details of it.

This is how i started it.. Outlines in HB .. started from the hair.

From hair to eyes and nose..

then moustache and jaw..

Finally

Karthi