Science of a Good Character:
Ever heard of serotonin? Without getting too "sciencey," it's a chemical in the brain that affects behavior. High serotonin levels cause a calmness, serenity and resistance to change. Low serotonin levels cause edginess, risk taking, and desire for change. Now the interesting stuff: In a study of monkeys, it was discovered that the monkey in charge, the "alpha," has a very high level of serotonin, and the lower members of the hierarchy have lower serotonin levels. Not only that, but the level skyrockets within minutes of taking charge. Now, what does this mean to us non-monkey writers? It works the same way with humans. When you get to the top, you stop worrying so much and you don't take as many risks as those under you. And those lower on the totem pole are more likely to have the desire and risk-taking behavior to take over and have their serotonin levels rise.
In stories, we want our heroes and villains to be active, fighting for change. Usually, a villain was once in charge and lost it--a big motivator. And a good hero, generally, has never shown up on anyone's list of most powerful people. Why is this? Serotonin. Here's the upshot of all this science: start your hero down and keep him down till the end. Those that are in power will be more complacent and not willing to change. Think of Jaws, for example, the Mayor is in charge and really doesn't want anything to change. He's complacent and way too calm for the situation. The Mayor's teaming with seratonin. Meanwhile, our hero Sheriff is a small town guy who no one really respects. He never gets respect or moves up the ladder until the end when he defeats the bad guy. Keep your hero down and keep him there. It's not just a good character tip, it's good science.