>>23535091First try to figure a corner in your picture which the light comes from. You'll notice that in
>>23534866 the light comes from the upper right corner, so the shadows must be drawn in the lower left corner of most things. Drifloon is the clearest example.
As you separate things with lines, usually you draw shadows where these are, like in Gardevoir's left arm.
How intense are the shadows depends in how close is the origin light and how glossy is the object.
I use a base color, shadeless layer placed behind the lineart.
In most layered (at least in both GIMP and SAI) programs, you have an option to make a "multiply layer" I put above the base color layer. (Look in Pic Related at the right, it says "Mode: Multiply")
Multiply layers take the colors behind it and multiplies them for a factor (Color / 255, which always darken that color). I always use a gray tone to do it. If I use a (128, 128, 128) gray, the colors behind are halved. That saves me the work to choose a darker tone for each color I used in the base.
Then I place a lighting layer above everything. This is, instead, an "additive layer", which works in a similar way to the multiply layers, but instead of multiplying values, they are summed. Use a near-black gray for soft light (like in the rightmost part of Gardevoir's left arm) and a lighter color -strong light- for drawing glossiness (important when drawing eyes or glossy things like hair highlights)
To avoid having problems I use the Base color shape as mask in both layers.
Hope that this helps!
>>23535424Here you can get a digital version of the book:
http://www.alexhays.com/loomis/Andrew%20Loomis%20-%20Fun%20WIth%20a%20Pencil.pdf 