I feel fairly confident in drawing the lines.
I know I need to work on it but at least with the line drawings I know what I need improving, where I've made a mistake, to frequently look from a far and as a whole to compare the ratios etc, and needing to improve more arm control generally.

But then I start shading, I have NO clue what to do..
I often don't want to start the shading and toning part as I know I'll ruin it. So a lot of my drawings remain looking flat...

can someone help or give some clues

here are some images of a drawing
http://i.imgur.com/xBrua.jpg
http://i.imgur.com/RW1nv.jpg
http://i.imgur.com/inw0D.jpg
http://i.imgur.com/ylFSE.jpg