The Getty Museum has this wonderful drawing, The Invention of Drawing, which documents one method of drawing. Illustrated here is an artist tracing the shadow of her model. Notice how the drawing is a precise rendering, done in two-point perspective. A single flame provides the light source for all of the shadows. The drawing contains a full range of values, from lightest lights to darkest darks. The horizon line, or eye level, is low, almost, if not exactly where the pencil touches the wall. Perspective lines are dramatically featured in the wall-mounted shelf, the lines of the furniture, and the stone wall grid.
Perspective drawing is a method of representing the appearance of objects, places, architecture and even people. Parallel lines are represented as converging, which gives the illustion of distance. There are many valuable sources to which one can refer in order to understand perspective. The following link is one good example that covers the basics of linear perspective.
The Invention of Drawing (recto); Sketch of Lower Leg Bones of Human Skeleton (verso)
Belgian, about 1791
Black and white chalk on brown paper (recto); graphite (verso)_21 1/2 x 14 in.