I first do a couple of thumbnails of two different compositions, then let the client choose and before cleaning up the sketch I block in roughly the lights and shadows. I always have a window with a smaller view of the image so that I can see it can be read well from afar.
For example here the blue light of the screen makes it easier to read the black silhouette of the character. At the same time, the orange light helps define his shapes on the left side too.
Long story short, I sketch it in but always keep changing things thinking about what would make the illustration more easy to read. Hope this helped!
It does, thank you! Sorry for the late reply--it's been a week. <><>
It's interesting to me how your main concern seems to be using the lighting to increase readability. I'll have to see what I can do about putting my own spin on the concept and using the idea in my own work--if Photoshop ever lets me use my tablet again/I can actually manage to find time between jobs. Either way, thank you for the information to help me along my artist's journey.