When you first approach a drawing, think about using contrast to make the picture interesting. Many succesful pictures are based simply around the concept of placing two things together that have great contrast between them.
There are endless contrasts to exploit: big vs. small, mechanical vs. organic, rough vs. smooth, etc.
Click to get a better look.
Many pictures that play on big vs. small have the big subject on one side and the small object on the other. That would seem to result in an unbalanced composition, but it doesn't when you do it right. In this famous painting, the fact that Christina's face can't be seen makes her a little less interesting than if she was facing us. The result is that she doesn't become too interesting in comparison with the buildings. Also there is a lot of detail on the house that's on the right and detail tends to draw your eye and also serves to give the house more visual "weight" than if it were just a blank silhouette (like the structure in the center). So even though the house is smaller than the girl it has just as much visual impact.
The way the detail is balanced in the picture is really nice: the girl's dress is very simple - just a pink open shape, free of detail - and it's set against the busy texture of the grass. So there's contrast between simple and complex areas that's pleasing to the eye. Then the grass detail ends so that the house becomes set against a blank plot of ground as well as a blank area of sky. So the house detail creates a complex area against a simple area as well. And having that happen on both sides helps to balance the picture too.
Cover the house in the middle with your hand. Now the picture doesn't work, right? This picture is actually based on a triangular shape. Your eye goes to the girl first, and then to the detailed house, and then drifts over to the central building, then back to the girl and through the circle again (so you could call it a circular composition as well, I guess). When you remove that middle structure, your eye goes from the girl to the right-hand house and then slides off into the sky at the left and off the page. Very unsatisfying! This picture (like all good pictures) does a very good job of controlling the way your eye experiences it. The way her body is placed to lead you into the picture is really cool. Her leg and arm pull you in and thrust you into the picture, and her other arm supports her so she feels solidly placed and also provides the accent that makes the sweep of her body work. And the fence and tire tracks do a great job of keeping your eye from shooting off the page, yet they feel entirely natural and organic.
In general - and this is really a loose rule - it's better to keep bigger objects closer to the middle of the page and smaller objects can be further away, closer to the sides. You can see how having big objects near the edges of the frame can make the picture feel like it's going to "tip over".
More on this to come.