It's a good practice to judge your representational artwork based on your drawing, the values and the edges/perspective. I think a skillful drawing is a foundation of a pleasureable artwork.

My charcoal drawing process is basically drawing the piece at least 4 times. After the vine charcoal, I start rendering the image with 2B charcoal. I find with charcoal that I almost always alternate charcoal and stump, or sometimes, just draw with the stump for soft markings. Again, always comparing the relationships between shapes, values, etc.

A.) Instead of drawing bold contour lines, I prefer creating edge lines by sketching the darker area next to the lighter area; the lines are not so hard and distracting. It's difficult to avoid drawing bold lines though, but I try to minimize as much as possible.

B.) Remember to soften your edges with the stump, especially when drawing flesh.

C.) For defining veins, I prefer to sketch the darker parts instead of just one line and then go over it and softened with a stump. While sketching your lines, always keep in mind the shapes of what your doing. For instance as in image C, the sketch lines I did for the veins follow a tubular shape to give that illusion of veins under flesh, especially after you soften those lines.