Edges
Space/Form
Light and Shadow
Proximity/Relation or Composition
Blind Contour
Continuous line drawing
No looking, one line only (don't pick up your pencil)
Lines that go across the object to show how it is 3D using only lines, no shading
Don't pick up your pencil
https://youtu.be/UXYAcjjNgQI
Work on proportions!
Outline shape of shadows and highlights too!
Start with the darkest shadows.
Build up shadows and middle grey tones.
Add white highlights by erasing or adding white pencil.
(Make sure to have black blacks and white whites and every tone in between!)
Visit here to learn about how to add shadows and highlights: https://thevirtualinstructor.com/shading-techniques-basics.html
Chuck Close (Photorealism)