well it's not that hard, study something study how it works and how your body works it helps you understand what a bady can do and what it can't do, when your done drawing something always ink it, it makes it look nicer and is easer to color with than just pencil
And add a light source to your coloring, you can't just put the shading and higlights anywhere you wish because then it looks unnatural and strange, and when using colored pencil change the pressure you use so you get the smooth light to dark look and it's looks natural too

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