What do Rocky Balboa, Dorothy Gale, Luke Skywalker, and Katniss Everdeen have in common? Other than the interesting fact that each character's name has a symbolic tie-in to nature, the answer is they're classic examples of "underdogs."
No, I'm not talking about flying canines in red capes. I'm referring to a useful way to build sympathy for your character. Think David and Goliath, cornered gazelle against rampaging lion, Cowboys versus Aliens. To get your audience rooting for your protagonists, sometimes all you need is to put them up against vastly overwhelming odds.
In the Hunger Games Suzanne Collins effectively uses this technique not only with her major characters but also with minor ones. Take Rue, the diminutive contestant from District 11, for example. While Katniss Everdeen and Peeta Mellark are preparing for the bloodshed and destruction of the gladitorial-like Hunger Games, Rue shadows them from practice station to practice station. Katniss notices how Rue looks like "a bird ready to take flight," realizes Rue couldn't "tip the scales at 70 pounds," and broods about how the small girl will be up against "a 220-pound male with a sword." With a few masterfully chosen descriptions, Ms. Collins garners immediate reader sympathy for Rue.
How about Rocky Balboa versus Ivan Drago in the fourth installment of the Rocky films? Ivan trains with hi-tech machinery, has an 1800 pounds-per-square-inch punch, and has already killed world champion Apollo Creed in the ring.
Overwhelming odds equals underdog. Underdog equals sympathy. Find a successful story, and you're likely to find an "underdog."