I'll admit that many of my stories tend to be "plot-driven" instead of "character-driven;" that is, my focus is more on the events of the story than the characters. As a result, I have to be careful that I avoid the pitfall of creating "stick figure" characters whose sole reason for existence is to have the plot happen to them. This is the difference between character and caricature. The best solution I know is to try to present character as if they were real people. When I speak of caricature, I'm thinking of:
- One-dimensional figures, either all strength or all weakness, dependent upon their role in the story. Usually this would be one strength or one weakness, focused upon to the exclusion of all else.
- Figures who behave unnaturally (say/do things that "real" people wouldn't say/do under the same circumstances), just for the sake of keeping the plot moving. You'd never see anyone act like these figures in real life.
- Figures to whom the readers cannot relate because they are too disconnected from reality.
- A combination of strengths and weaknesses, likes and dislikes, products of their background and experiences...just like real people. You probably can't delve into all of these things, but there should be a sense that these dimensions at least exist.
- Figures who react to situations in a way that would be expected of real people. They don't have to react the way that the majority of people would (we're all different, after all), but their actions have to at least be believable, something that at least would not be unheard-of.
- Figures to whom the reader can relate in some way because they, while fictional, have some roots in reality. The reader needs to be able to think, "Hey, I know people like that," or, better still, "Hey, I'm like that" or "I could be like that."