Drawings may be coming soon.
Draw a picture, and do NOT thicken the lines of wrinkles on the body or clothes, and plan what colors you want to color to color the picture with. Find where your light source will be on WITHOUT COLORING YET. Draw a line around those parts. Now find the part where you want to make the color a little thicker. Make a line/dashes/dots/etc around that. Then do the same once more. Make the lines look different so you can understand what colors you want differently easily. Fill all those in.
Note: Anything that looks inward (like a hole), depending on your light source, MUST be darkened on the inside. Sometimes you don't want it very thickened though.
Note 2: I mostly know how to darken with just pencils; though this is a way I learned. Another way is doing it the opposite way: Start shading darkly anywhere that's NOT your light source, and start getting lighter to find your light source.
Note 3 (some-what helps with shading mistake): What /some/ people do that's odd, is make one part very light and one part very dark, which makes an image look odd. If you make this mistake (mostly done with crayon), I suggest to try to erase the middle of the both in between. Like if one part is light red, and another is dark red, go to the middle, and smudge it together.
PS: When doing this, I would try smudging the dark red side /to/ the light color side. Why? Because if you just erase the middle, you'll most likely be erasing the middle, and ruining the coloring.
Note 4: "But what do I do if I have two light sources?" you ask? Well simple. Do what I did at the top. This might end up like pillow shading (where your source is at the middle of an image and there is no light source defining it. Hop showed an image of this, credits to Makkine)... the other way around. Do what I did at the instructions WAY up there, but find all two light sources.
PS: Imagine a ball. Two light sources will mean one side is light and another side is like, but the center of the two might be darker.
Any questions? Just ask.
This is /my/ style of shading with /crayons/.
Btw, I don't expect people to read all of this, so if you do, congrats, you learned something from me. xD
Note: I posted this in someone's topic by accident. If you noticed that, then... o3o sorry to the topic maker?
Still improving everyone