Don't neglect the background forms or off-form shading! Make use of cast-shadows and invented shading to provide spatial cues.
Using graphite or charcoal pencils on drawing paper, complete a four-part drawing of a pair of shoes using a single sheet of 18 x 24" drawing paper. Divide the paper into four equally sized cells and:
complete a gesture in each of the four cells,
overlay three of the gestures with volume summaries,
overlay two of the volume summaries with organizational line (Giacometti) drawings,
and apply linear shading and enhanced line quality to one of the two organizational line drawings.
Be economical and judicious in your use of linear shading. Tidy up the drawing, removing the searching lines.