021 Workflow of imaginary sketch and shadow explanation

I do lots of sketches from imagination (mostly in pencils) next to doing studies, as they let you apply what you learned. Here is a little step by step workflow of how I do that (description below):

Steps 1-5 are done with an HB pencil, 6 uses a 2B and 7-10 alternates between the two as needed. For final details and dark accents, I also use a 6B pencil sometimes

1. Establish a horizon and a basic perspective grid
2. Gesture: Here I either have a concrete image in my mind or I just try out different gesture poses until I find something I can work with or that gives me an idea about a character. In this example I wanted someone jumping and with this pose, I got the idea of somekind of assassin/thief jumping down with a dagger.
3. Building anatomy: here I correct errors and establish a basic anatomical model with a Loomis head.
4. Once the anatomy is ok, erase everything slightly, so it is barely visible. Now the fun part begins. I mostly start with the face and try out some basic design ideas. The base clothing is established
5. Detailing and design step: here I put everything in place designwise. This step uses the visual library in my head that was established through studies (and it is ever growing). Here the clothing is very basic and simple, but anything is possible. In this step your creativity can do whatever it wants, using historical clothing, clothing from movies you have seen, combining them, anything...
6. Cleanup: the lines are cleaned up and some line weight is incorporated

7. Base value step: here different values for materials are done. I only have 2 values in that example,but it can be more elaborated depending on how detailed and realistic you want the finished drawing. This is not shading, it only shows how light or dark the material is!
8. Basic form shadow is applied
9. Cast shadows are applied
10. Occlusion shadows are applied and some more detailed shading to finish the sketch. A cast shadow below the figure keeps it grounded.

Different forms of shadows:

Shadows are really important in a drawing, in my opinion even more important than the values of the lights. A well placed cast shadow and some occlusion shadows can make a drawing pop and give it a more realistic look.
So what are these different kinds of shadows? Basically there are three different forms of shadow:

1. Form shadow
2. Cast shadow
3. Occlusion shadow

Form Shadow:

This gives a shape the illusion of a 3-dimensional form. Basically all planes of an object that are hit by light are called form light and everything of the object not hit by light is form shadow.
With only one light source it is usually easy to spot, with more it gets more complex...

In the example below (Nr. 3) the cylinder is lit from straight above, so as the surface curves away, it gets darker until the surface and light are parallel to each other (this is called the terminator, the breaking point between light and dark). Here no more light can bounce of the surface and the form shadow starts.
Form shadow is actually only one value, but as light bounces of other surfaces in the environment, some light is reflected back into the form shadow. this is called bounce light and can be seen on the bottom side of the cylinder. The value of bounce light never gets lighter than the darkest value of the form light!

Cast Shadow:

Any object hit by light casts a shadow onto other objects (or even itself). These shadows mostly have a sharp edge and they follow the form of the object they are cast upon. (below in Nr. 4 you can see the shadow cast by the cylinder above following the form of the cylinder below)
To draw them can be tricky. It is possible to construct them ( Scott Robertson How to render is great in explaning that), but mostly I eyeball them in, using my understanding of forms and volumes. The edges of cast shadows get softer the further away from the casting object they get.

Occlusion shadows:

These shadows are the hardest to get and they are often overlooked. But implementing them into your drawings can make them really stand out! Basically, occlusion shadows occur when two surfaces get closer to each other as they block out the ambient light. This is why corners in a room seem to be a bit darker than the walls.
Below in Nr. 1 and Nr. 2 you can see this concept.
These shadows are also called contact shadows. A good example of why would be a person standing on the ground. Where the shoes meet the floor, you always have a darker edge.
Occlusion shadows are always soft! Draw them with a gradient in mind, starting lighter in value and darkening them down  (like in Nr. 2)
They also not only occur in touching surfaces angled like in the examples below, but also on surfaces next to each other that do not touch  (like two legs on a standing figure for example)
If you´re unsure whether or not occlusion occurs, imagine rays coming out of a point on a surface going in all directions. If these rays somewhere hit another surface, occlusion occurs. The closer the other surface is, the darker the shadows are (so there might technically even be occlusion that is not visible at all, because it is so subtle....)

Hope this is useful!