Crosshatching is an effective way to create values with lifework. Here is an example of using this technique to suggest depth in a sketch of Yosemite Valley with a Bic ball-point pen. Click on the first image to start a step-by-step slide show.

Use contour shading to show the planes of the cliffs. Yosemite Valley runs East-West so the North-facing slope is in shadow while the South-facing slope is bathed in sunlight. Note how the pen strokes can suggest the planes of the rock faces. Lighten your strokes as you move to the background elements.