It is very important to understand the construction process of basic geometric forms and chiaroscuro shading pattern application.

Chiaroscuro is a method for applying value to a two-dimensional piece of artwork to create the illusion of a three-dimensional solid form. 
This way of working was devised during the Italian Renaissance and was used by artists such as Leonardo da Vinci and Raphael.

1. Highlight is the lightest value of an object. This is where direct light hits the surface.

2. Light - as the surface curves, it does not get as much light, so value becomes slightly darker.

3. Shadow - once the surface curves away from the light source, it does not receive any direct light, but it does get some indirect light from the surroundings - that's why it is not completely black.

4. Reflected light is light that is bounced off the surfaces (surroundings), making the value slightly lighter.

5. Cast shadow is the darkest value, but further it is from the object - lighter it gets.

cube

Start with the front corner line. Draw 4 receding lines going to the right and to the left. Use intuitive perspective.

Define the far corners.

To create the top side - draw two receding lines going the opposite directions.

Draw the back corners (that are hidden) - imagine that the box is made out of glass or clear plastic.

Imagine the light sours in on the left. Apply chiaroscuro pattern to shading:

1. The left side will receive the direct light. It will be the lightest value.

2. The top side will get some light - it will be slightly darker than the left.

3. The right side does not get any light from the light source. It is in a shade. This side though receives some light, reflected from the ground surface (4 - reflected light).

5. Drop shadow is the darkest value of all, especially closer to the object.

Shade the darkest values first.

Create the biggest contrast next to the corners.

sphere

cylinder

cone

pyramid