I think the main issue with this one is that you are not sure where the light comes from. When I look at it it seems it comes from the top, but also from both sides and in other areas none at all. When shading a drawing always decide on the light source first. I would limit it to one + rim light for starter. Try to shade basic shapes like spheres and boxes for practice - it will give you better feeling for shading more complex forms (see A). Color choice also matters. You seem to pick dark/light shade of the same color for shadows and highlights respectively which makes it look so muddy. Try to change hue as well (see B). Never use white color for highlights unless when touching up finished drawing - otherwise you will have no room for even lighter areas. Shading heavily depends on style, but for starters I would suggest using hard round brush and airbrush(see C) as well as manual blending (look it up). Vary soft and hard edges based on distance between objects and light intensity - when an object is close to another surface it drops darker shadows with sharper edges (see D). Skin rendering varies based on color of the skin but generally it is not all the same tone. There are parts that have better blood flow and thinner skin (nose, ears) - they appear reddish/orange. Skin in the shadow (cheeks, neck) might have cooler tones (depending on environment and lighting conditions). I would suggest looking up skin coloring tutorials as well as real life references. Don't be scared of highlighting surfaces and details. Hope it helps. Good luck! | Artwod Feedback