I've always found Campbell's Hero has One Thousand Faces somewhat inaccessible. The information's buried so far down in metaphor that I found it very difficult to apply, as a novelist. And Vogler's Hero's Journey's not much better. I did, however, come across this piece online the other day, which explores the same material but makes it somehow more digestable. It's a lengthy read, but worth it, if you're looking at story structure and character arcs and trying to make sense of your gut feelings about things.

The writing game's pretty simple, really. Take a story, either one that you've written, or a book you've read recently, and find the points of the journey, if you can. Now, not all stories follow the journey (though they can usually be shoehorned in if you try hard enough, just as any literature student). The point is to get practise at seeing the structures so you can internalise them.