My first pixel art so far. Not sure what to do for the shading

This is my first pixel art I am working on but I dont know how to do the shading right. I did some bits and pieces but im stuck on the shading. Some criticism to lead me in the right direction would be appreciated

Well if you need some starter instructions, these sources should be of help

Pixel Joint Forum: The Pixel Art Tutorial
Pixel Art Tutorials - The complete Pixelblog catalogue — SLYNYRD