just thought gonna drop some info here about how to determine where are hard edges and where they are soft.
Try learning planes of the face with Asaro Head. There are loads of pictures online and even 3d models.
So basically, you need to figure out what planes of the face receive most of the light and what planes receive less. And building your values correctly in the picture will also help you with making objects appear more 3-dimensional.
Don't know what else to add, I personally learn a lot by observing things (photos with good light setup, masters works, artists that i like - i turn everything in greyscale and analyze how light shapes up the form of an object, i think through about where are the lightest and darkest points etc)and i also try avoiding blackest black. I go near it but never 100% (or at least i try) same with white. Reflection cannot be brighter than a light source, unless the object is very shiny.
Here's also a 2hr video about light, edgework and smudging
Hope it helps, or somewhat useful