Working on faces

In my last tutorial John suggested that I work on my faces more and really look at them. 
I have been looking at the dust jackets and I've found drawing in pencil helps a lot more than 
working in pen, they're not there yet but I will keep looking and referencing and then hopefully transfer this into some of my scenes. As I have been working with ink in the backgrounds I think it will look 
ok to draw the faces in pencil but I need to try it out.