You did a good job at greating the proportions right on the facial features, they are placed where they are supposed to be on the face, so good job there.

I can see that the left eyes is a little smaller and off angle to the right eye, to help with that tricky symmetry I use a mirror to help check myself. Perhaps you would find it useful as well?

The top of her head bothers me a little though, she almost has a cone shape to it, by drawing a perfect circle with a line halfway and than drawing the jaw from the that halfway point. You will get a pretty solid way to get the head. Though of course there are many ways to start, but you may find it useful .

When it comes to shading it is always good to get a nice tonal range of lights and darks, black being the darkest and white pure paper. This ensures that your form is strong and you create believable volume. The pupil is generally the darkest part so that has the added bonus of bringing the focus to the eyes, the window to the soul.

When drawing hair, I find it helpful to block of the locks of hair and treat them as individual pieces to shade. That way you get the texture of hair down without drawing every single strand. This also gives a lot of life to your drawing.

Hope you find this helpful, and keep on drawing