This light tutorial should have almost everything you need, though its focus is more on how light works and how it affects colours, it doesn't talk about how to figure out cast shadows and composition.

There's much more to a light source than a direction. How large is it? That affects how much of the character is lit, and what sort of shadow(s) they cast. How intense is it? That affects the intensity of the light on the character/scene. How reflective is the environment? That affects how dark the shadows are, if the light bounces a lot, the shadows will be lit up too. Even just directions are complex - don't forget that your scene is 3D, which means your light source is positioned in 3D space relative to your character. It's to the right, but is it also behind, in front, above, below?

Added the ground, a little update :)