Dodge and Burn are your enemies. If I were you (which I am not) I would take the first step towards great coloring now. You simply need to remember this basic tidbit of color theory:
Yellow=Highlight ; Purple=Shadow
I'm not saying to use pure yellow and purple to shade (though you most certainly could for a dramatic look), but when you're choosing highlight and shadow colors, try to move you color selection slider at least a bit towards those tones to add some depth and realism. Also generally shadows are less saturated in color than midtones or highlights, that is they're closer towards grey, so by using burn, which not only darkens the color, but also raises saturation, you're really messing with how shading should work.
As to the structure of your shading, establish a light source (half the time I'll draw a lightbulb where my light is coming from) and draw invisible beams in your mind to see which parts of the face would be hit with light. Right now the face looks very flat with the only form establised is beneath the eyes and on the cheeks, be sure to shade the contour of the chin, the depressions from the nose to the corners of the mouth, the shadowline under the nose and the shadows created by the hair. Right now you have highlights directly under the bangs, which would instead be casting heavy shadows.
I think you have potential, but are starting down a line of coloring (encouraged by anime art no doubt) that is completely unrealistic, break away from that early and then you won't have huge problems changing years down the road.
Edit:
I learned HOW to shade by my art teacher telling us to paint a cow skull on black draping fabric and locked all the black and white paint away. All we had was red, yellow and blue. It works.