I'd write a huge detailed post but my hands tell me that i have to not be very wordy, so here's some visuals that i hope you don't mind:

As for lines... Well, practice, i guess. I've found that fast motions makes lines less wobbly when freehanding, but it also reduces accuracy. That is why we have undo. :U
You did pretty well with the face though, fairly accurate proportions there (cartooniness besides).