All forms are seen basically arise due to differences in color.
From this basic law that allows us to make various impressions on paper using a pencil.

By taking the black in terms ranging from 0% to 100%, this will be the main points to make the images in Grayscale.

A perfect image would be created if some of the points above are met.

shape & scale appropriate original shape.
Perspektif from the viewpoint
Contras (black-white differences in Grayscale)

It surely can be achieved by doing a lot of practice.