Help me with my drawing of Natalie Portman?

I had an urge to draw er yesterday & since it's the summer I can't go to my art teacher for help :/ I started off drawing her at the 2009 oscars & then changed her hair to the better known pixie crop she had & changed her features to make it more obvious it's her. I did this with an average writing pencil, I can't find my good HB or my graphite pencil anywhere. So yeah, help me make it more realistic? What is missing? I'm 15 by the way & I know I'm not particularly amazing at drawing but I really want to make this look the best I can :3 a href="http://m.flickr.com/#/photos/38815014@N06/5876292261/" rel="nofollow"http://m.flickr.com/#/photos/38815014@N0…/a (I don't a scanner so this pictures doesn't really do it justice)