When cooking up a main character, there are a few basic ingredients and everything else is garnish. In general, you want to create someone who is both empathetic and altruistic, someone who most readers would aspire to emulate. Your MC will usually be a hero, but should not be a hero caricature, even if he's Superman. One of the easiest and most critical ingredients in hero creation, and thus one of the easiest to abuse and overuse, is attitude.
Most people, when faced with conflict or adversity, may put a step forward, but ultimately, will shy from even ordinary conflict to maintain a peaceful existence. To push story forward, however, we need conflict, characters who won't back down from danger, from doing what's right or wrong. This requires a strong sense of self, a strong attitude.
Now, we can easily stray into the realm of hyperbole, but think of your favorite books and you'll probably recognize that the MC's attitude is more internal, more what most of us aim for -- the Teddy Roosevelt approach. Similar to plotting, create your attitude more through action and and less through dialogue and introspection, which is what I call overt or cheap showing (hence that aphorism: actions speak louder than words) - sometimes this is necessary or natural, but action's the meat and potatoes, and your readers aren't on a diet.
PS - if you're writing an anti-hero, your MC should have a similar attitude quotient, his motivation's just on a different axis.