After the line drawing is done, it's always gratifying to add realistic shading to it. Shading makes the subject look three dimensional and solid. Here's an easy technique with instructions and a practice lesson to help you learn it.
Before you Start - How to Hold the Pencil
Use an overhand grip for these exercises. (Shown in the photo to the right.) Fill a sheet of scrap paper with broad marks made with the side of the lead until you're comfortable working with a pencil held this way.
B or HB Pencil
I used a Derwent B Drawing Pencil and Canson drawing paper. Here they are at Dick Blick: