Other than what @malcom already wrote, when your at the rendering stage, you could also try to start by blocking in the lights and shadows in a very defined way. Kind of like a cel-shaded style in comic books. I think it's a nice way to start defining the forms when you're starting to render.
I've made a rough example just to show what I mean. And you don't have to make the inked outlines. I just made that to make the drawing clearer.
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From there you can just start softening the transitions and add some color variation as needed.
Hopefully this helps you. Keep drawing!