Make sure you err on the side of the dark.
Keep it in midtones, then put in the darkest darks, then put in lightest lights.
There are thousands of different ways to render form. It doesn't need to be 100% accurate all the time. Just make sure it looks cool.
Keep things loose until the very end. Always.
Its about corners and highlights. Those are the hardest and show the most form.
Render the major plane changes at a time.
Sculpt the form as quickly as possible. Leave the planes simple, then go in with the divets and veins.