General unrequited tips on sketching: Shade more. Shading is scary at first! But shading makes things more dramatic and less washed-out. Resist the urge to smudge the graphite with a finger or overuse a tortillion. Blocking with a light touch using the hardest pencil you have is a good idea, especially when you're training your eye.
Looks like you have a knack for sketching. Keep practicing!