Michelangelo 2

Trying to practice the pencil shading skills.  This is MUCH harder than I thought it would be.  I've been looking at some the artist who have a style I'd like to implement, and I think, yeah, that looks simple enough.  Then I sit down to practice and it's train wreck after train wreck.  I'm especially mad because I've wasted so many otherwise decent line drawings.  I think I'm finally starting to get the gist it, but I just don't when use cross-hatching, straight-hatching and so on.  Still, I think I'm slowly getting better.  Any of you out there with tips or pointers, I'd greatly appreciate it.  I'm trying to grow as an artist, and growing pains suck.