Ugh, faces are the bane of my existence so I don't have any advice for that. For shading though, unless you're going for a semi-realistic style, I'd get rid of the hard outlines. You can get pretty close to realism with thin outlines, like with this drawing:
But, ideally you'll want to define edges with differences in value, like the jawline on this portrait:
Also, don't be afraid to go darker in some spots of the figure. I'd say a drawing aiming to capture real life should have all range of values, from the whitest white to the blackest black. Without a having a strong white and strong black, a picture will look flat and dull. A picture with strong white and black without a lot of mid-tones will be dramatic and energetic, but might be too dramatic for what it's going for. Here's a good post I found here on DeviantArt about tone: A Brief Discussion About Tonal Contrast
Since you're using charcoal and graphite, I suggest getting an ebony pencil (it'll allow you to get darker than charcoal) and white charcoal (since it looks like you use toned paper). Tone paper's awesome for shading, but it's good to have a tool to put white into the drawing. If you're really adventurous, try out some ink to get even darker than ebony. It's hard to tell if you already use this or are really good at blending away pencil marks, but try out powdered graphite and charcoal with a brush. It speeds up shading big time and can save hours on bigger drawings.