Draw a still life twice, and do not use an eraser. This exercise will take up 2 pages in your sketchbook.
Leave in all your organizational/process lines. In your first still life, use organic/curving organizational lines (note the rounded organizational lines around the fingers and ankles in the sample images below). In your second still life, use angular organizational lines (see the last image).
Make sure that you fill the entire page with each drawing (avoid small in the middle of the page). Show evidence of time invested – it is very easy to tell when a student has spent 10 minutes on a drawing versus 30 minutes.