Great quote from Alvin Sargent in the most recent [Written By](http://www.wga.org/writtenby/writtenby.aspx):
> Somebody told me once, “If you have a problem with a character, give the problem to the character because it’s not my problem.” It’s truly their problem and you have to watch and wait and see what they do that makes some kind of sense. Sooner or later, if they are really people, they will do something, or someone else will come and help them. But I have nothing to do with it. If you have a problem, give it to the character.
Characters are not responsible for plot; you as the writer have to decide what you’re showing, when and why. But your characters need to be responsible for the actions they take. The reader and the audience can feel when characters are doing something simply for story’s sake.
Think of yourself as the producer of a reality show. You’ve hopefully cast interesting people, who will do and say interesting things. You’ll create obstacles that will force them to react. You’ll shoot a bunch of footage and edit it to tell the story you want. But if you’re pushing your characters around, telling them exactly what you want them to do, the audience will feel the manipulation — and your characters will resent it.