Introduction to Pencil Shading

When shading an area, the first thing most people do is to move the pencil back and forth in a regular pattern, with the 'turn' at the end of each movement roughly parallel, as in the first example. The trouble is, when you use this technique to shade a large area, that even edge gives you a dark line through your shaded area. Sometimes it is only subtle, but often it looks very obvious and spoils the illusion that you are trying to create.