Thanks a ton man!
To be honest, I focus both of these in my studies. I will give you a sort of overview on what I do, and pardon me it it's not consistent.
As I was studying, I realized that there are so many different shapes I can see in the reference, created by lights, shadows etc. Some shapes are more prominent, while others more subtle. This has to do with what type of lights or shadows you got ( ex cast shadows have sharper edges and are more defined ). I focus on identifying and creating the bigger shapes first, and then I focus on the smaller ones in certain areas. This is good since these shapes have edges/angles, which can be used as measurement / comparison points. I recommend always focusing on bigger shapes with one value and then going smaller and focusing on areas.
On the other hand, while I work with blocking in shapes and corresponding values, It is important imo to have an idea of the underlying construction. Construction acts as a guide on how you can place your shapes, strokes etc. I do use a bit of line/sketch to have an overview of the underlying structure ( basically I did a rough mannequin as I blocked in shapes in a different layer ).
I also try to pay attention to different angles created by negative space. It would be a lot like "focusing on outline", but I think it is different in this case, since you have construction already in mind.
Finally, I work with very low contrast, separating light and shadow, and go darker and lighter slowly. I use dodge/burn and adjustment layers a lot as well. Since this was a value study, I would color pick areas to see if I did correct, and if not, I'd fix the value, which helps me see more subtle transitions as I go.
PS. always change the brightness of the background from light to dark so you see how well different value groups read.
Hope I helped mate! Let's keep all doing awesome work!
