OK now we are going to start doing some master studies. When doing a master study the aim is not just to copy the image but try and understand how and why they did things. For example look at the way the lighting and shading describe the form. Look at the way the shading lines or brush strokes shape the form. Look at the types of curved lines etc they use to make the anatomy look more organic and natural. If you do these studies correctly you will learn a great deal.
Also a quick note. A lot of these drawings will be done on toned paper using white and black chalk. And some will also use Conté Crayons. Doing it this way lets you get the 3 or 4 values you need to describe form well. I would suggest if possible to get these supplies and do the drawings in the same way. I will try if I ever get a camera and the time to do a video tutorial on how to do this. But until then start with your mid tones and light shadows then put in your darker shadows. Then if all of that looks right put in your highlights to really make it pop:)
The first master copy I am going to have you do is this one by Annibale Carracci.