John Asaro Planar Bust Style Adam Bust: Planar Hybrid Head, Art Reference or Modern Decor.

I like the asaro head since it lets you see the planes very easily and you can position the light source any way you want. I'd practice construction this head and the facial features from multiple different angles, then immediately jump into a portrait study where you practice breaking that reference down into planes. Just make sure that you understand that you need to mold the planes to fit the reference and not the other way around. As for form with shadow shape, try doing 2 value studies: where you only work in 1 value of light and 1 value of dark. This will teach you how your shapes create form.