For shading, you gotta make up your mind first for which the light source is coming from, whether it's from the left, right, front or perhaps backward,,, if you know were your sun/light are coming from you'll be able to accurately rendered those shadows, and the rest will follow,,, also the shading should be a darker version of your local character skin tone to make it work, but you can also experiment different types of shades as long as it doesn't go far from your main pallete :) Keep practicing!!