As I want to create a loose, hatched look in this sketch, I've let some of my shading carry across the outline. I'll use the eraser to clean that up. Sometimes if you try to draw all the way up to an edge or outline, the marks will get heavier as you get closer. So this is one way to prevent that effect.
Don't worry about surface detail like spots or patterns - the object of this lesson is to create a fairly three-dimensional looking shaded form, showing light and shade. The focus is on 'global tone' - the overall effect of light and shadow - rather than the color and detail on the surface of the subject.