I know how your drawing can be improved. ^^ Sorry I had to post it here, I couldn't use DA Muro on the deviation page.
The head shape is a little irregular (don't worry everyone does this when they start out). This can be fixed by a certain technique that my friends and I use. There are a few steps:
1. draw a circle. It doesn't have to be perfect, but just make sure there is a sketchy circle.
2. draw the jawbone and the chin. If you look at any correctly-drawn anime character, they have a pointy chin, a jawbone (where their ears start) and then the head sloped out from there.
3. draw a straight line down the middle of the head. This of course will help you proportion everything.
4. draw a horizontal line halfway down the face. The middle of the eyes should sit on this line.
also, please bear in mind that I don't ever use digital software and therefore am not very good at using it. Plus i have a laptop mouse, which is a pain to use.