The other matter I wanted to touch upon is the issue of fur. It's very easy to get carried away with drawing fur textures, and most often it's really not necessary. Attempting to render fur will often result in a lot of contrast, which will create a focal point whether you want it or not. There are tricks, however, to imply the presence of a furry surface texture.
Instead of covering an entire object with fur, it is generally more effective to simply alter the silhouette of the object. This means applying your furry protrusions around the edge of the object. If you imagine that all of your objects were filled in with black against a solid white background, all you would see is its solid silhouette - and the only information you'd have to infer its surface texture is the consistency and quality of the its edge. This is the type of information that viewers will read the quickest, and the kind of information that will stick the most.
It's also the reason that the sort of rough, chicken-scratch sketching that you see from beginners is to be avoided. As you gain more skill, you realize that the weaknesses from your early days can be harnessed as tools - as long as you can control them, and apply them only when needed.