The biggest thing I can say is, work on keeping your lines smooth, right now a lot of them are looking rough.

As for individual portions:

Eyes - the shape of the eye is more complex shape then a football, and on women, it is best to draw them more open than you have them. Even though the eyes in the picture are partially closed, making it a little bigger will emphasize them.

Face shape - rather than use 2 tones to define the chin and cheeks, use a subtle gradient on the neck, darker near the top, then getting lighter towards the bottom, and do the same for the face, making it darker at the line were the hair is over the face.

lips - Look at a pairs of lips, and pay attention to the curves. They are subtle, but powerful.

Hair - I am not quite sure how to explain, but it should look more like strokes that come to a point, and the varying width depends on what style you want it to look like.


I hope this helps. I will try to make some tutorials on how to vector different parts of the human face.