The document discusses three shading techniques - shading, stippling, and crosshatching - that can be used to create the illusion of three dimensions on a two-dimensional surface. Shading involves blending pencil to transition smoothly from dark to light values. Stippling uses small dots to simulate shading. Crosshatching uses closely spaced parallel lines that wrap around forms, with darker areas created by more, thicker, and closer lines. Attention to light source and shadows is important for creating accurate shading.