I'd recommend using watercolour pencils... it means you can blend colours more, and get rid of pencil-strokes.
*Looks at picture without really focusing on it* I think it make it look more realistic, work on your shading. Perhaps more depth needed on the hair? And the darker strands are perhaps a bit too dark? and maybe the shading on the check is... um...
Basically, practise and experiement! It's very a very good picture - especially the shape of it!
