The best advice that I can give you in improving your drawing is the same advice that one of my college professors gave me. You have to "learn to observe the visual nature of things." What does that mean? Study the world around you and the way that things look. It is important to understand what you're trying to draw and truly look at it as if you've never seen it before.
Take a look outside your window. What does it look like out there? How is the weather and the time of day affecting shadows and objects appearances? What does a tree look like at noon on a sunny day? On a cloudy day? In the winter?
If you're trying to draw a chair, don't just draw what you think a chair looks like - look at a chair. Look at all of the various details about it - what angle is the seat at? What materials is it made out of? Look at its structure.
Take a look at things around you. How about that pencil? You know what a pencil looks like, but are you really seeing it for what it is, or are you just looking at it and labeling it "pencil" in your mind? It's a good exercise for sharpening your powers of observation. The more that you observe, the better your powers of perception of are. The better your powers of perception are, the better you will draw.
So, to sum it up - study, observe and practice.
If you are serious about getting your figures
to look right, studying anatomy is essential. I recommend taking
a life drawing and/or anatomy class. It's important to learn about the proportions
of the body
and its underlying structures. If an anatomy class is unavailable to you,
you may want to study yourself in the mirror or use a friend for a model.
Photographs can be helpful tools, but they don't always allow you to see exactly
how the body is bending/foreshortened.
If you want to draw anthropomorphic figures, I recommend studying the animal that you wish to anthropomorphize. Watching live animals at the zoo, etc, is great. Children's non-fiction books are also good, with plenty of nice pictures to study. An encyclopedia of animals or mammals is another great resource, if you can get your hands on one. Stock photos from the web can also work well if you're in a hurry.
Take a closer look at the animal you're working with. I did studies of ordinary squirrels, researched their subspecies, and their habits before I ever tried to draw Jody. This may sound tedious, but it really does help.
I cannot overemphasize the importance of finding good reference materials. Finding a good resource to work from is essential in many cases. Planning on drawing some people dancing? The best option would be to ask for permission to life draw at your local dance studio. Barring this, find a video of people doing the kind of dancing you want to draw. Still images aren't always as good for this, but you can check out a book on dancing from your local library or do an online image search for photos.
Imagination will only
take you so far. If you leave a pic of people dancing to your imagination,
the chances are pretty good that there are going to be some inaccuracies
in the figures' positioning and in other details. People tend
to notice these little things. Images that are technically accurate,
as well as artistic, are what "good art" is all about.