When I embark on a coloured pencil drawing I always like to concentrate on the part of the drawing that will attract the most attention.
The eyes are usually the most important thing for me but what is also imperative, is layering colours. Usually a picture like this will take me 10-15 hours because the more layers of coloured pencil that you use, the greater the depth and intensity of colour can be achieved. It will also make the subject more life-like.
