Coal Miner's Daughter
Our heroine hails from the desperately poor coal mining District 12, where she lost her father to an accident in the mines. It's the most destitute part of Panem. Fortunately, Katniss is a deadeye archer, and she supplements the family's meager food supply by shooting animals in the woods. Katniss is at home in the woods, something that works to her advantage later in the Games.
When survival is job one, you have to be a practical person—and our girl is just that.
For a child of destiny, Katniss Everdeen is actually a bit of a pill. She's not on a mission to save the world, like Gale, or just trying to survive like Peeta. She doesn't have a cause, she doesn't like being the center of attention, and all things being equal, she just wants to be left alone and do what it takes to keep herself and her family alive. So yeah, no time to hang out with friends or watch TV, even though her life turns into the ultimate episode of Survivor.
She Wants to Be Alone
Katniss's desire to be left alone is clear in the first few scenes, as she slips out past the District 12 fence to do a little hunting. She does it to get food for her family, yes (more on that in a bit), but she also seems to appreciate the solitude. Her hunting skills are of the kind where she can sneak up on you without drawing any attention to herself. As Gale tells her right after she's volunteered to be a Tribute, that means more than she may think:
GALE: If they don't have a bow, then you make one, okay? You know how to hunt.
We see that independence in the arena, as Katniss first heads for the hills, then engages in a slow game of cat-and-mouse with the Careers (the scary kids from Districts 1 and 2 who apparently majored in murderkill in school). She stays quiet and unseen throughout. The Careers get into a big group and go tromping through the scenery, but Katniss stays silent and picks her moments. Given her skill with a bow, that can be pretty devastating. (Seriously, between her and the Careers, who's still alive at the end?)
On a subtler level, her ability to sneak up on people can be more than just literal. She doesn't think of herself as a symbol, and she doesn't much want to be. Nobody can really spot when she goes from being an ordinary girl to an instant celebrity, or from a celebrity to a defiant symbol of resistance.
Well, except for President Snow, of course, who's a pretty paranoid dude and spots the kind of trouble Katniss represents very early. But instead of silencing it, he actually makes it worse by overemphasizing her importance.
SNOW: Hope. It is the only thing stronger than fear. A little hope is effective. A lot of hope is dangerous. A spark is fine, as long as it's contained.
SNOW: So, contain it.
Seneca, the game maker, seems to be blowing it off; Katniss is just one more piece of meat for the grinder to him. But Snow seems to see some danger in her, and he doesn't just mean winning the Hunger Games.
Selfless to a Fault
Katniss's other quality is something any good hero needs: a willingness to help others. Katniss isn't entirely happy about it, of course. She doesn't want to die in the arena; she just wants to keep living the way she has been. But "keep living the way she has been" involves looking out for her sister Primrose.
We see it even before she goes off into the woods, as she comforts Prim after her little sister has had a nightmare about being in the Hunger Games:
KATNISS: It's okay. It's okay. You were just dreaming. You were dreaming.
PRIMROSE: It was me.
KATNISS: I know. I know, but it's not. It's your first year, Prim. Your name's only been in there once. They're not going to pick you.
That's some serious big sister devotion.
And as it turns out, it's even more than that. Their mother appears to have checked out on life after the girls' dad died, leaving Katniss to care for Prim on her own. When Katniss goes off, she tells Mom to step it up:
KATNISS: You can't tune out again.
KATNISS' MOTHER: I won't...
KATNISS: No. You can't. Not like when Dad died. I won't be there anymore, and you're all she has. No matter what you FEEL, you have to BE there for her. Do you understand? Don't cry. Don't cry. Don't... Don't...
So it's pretty clear that Katniss is willing to go above and beyond for those she cares about, even volunteering for the Hunger Games to keep her sister out of them. No bigger sacrifice than that.
And it's not only immediate family. Once she's in the arena, people like Peeta and Rue become very important to her, to the point of risking her own life to keep them safe even though they may eventually be forced to kill each other. As she tells Peeta when he's injured:
KATNISS: I'm not gonna leave you. I'm not gonna do that.
Talk about dedication. I mean, we love our besties, but would we take a bullet (or an arrow) for them?
Katniss is definitely afraid of something happening to her family, especially her little sis, but when it comes to her own safety, she can be fearless. Of course, she's worried about dying in the Games, but it doesn't keep her from getting in the face of just about every authority figure she meets. She shows this early, by nearly impaling Haymitch's hand with a knife to get his attention. When Cinna tells her and Peeta about the flaming costumes, he says, "Don't be afraid." Katniss shoots back, "I'm not afraid." She's very convincing.
After the Tribute parade, she runs into the alcohol-soaked Haymitch and has one of the best one-liners in the film:
KATNISS: Are you sure you should be around an open flame?
As Katniss gets deeper into the Games, this cheeky attitude evolves into something much more serious.
Fight the Power
So here we have a self-assured girl who's confident in her skills at lurking and shooting things dead with a bow; someone who doesn't want attention and won't declare herself an enemy (and thus put a target on her back). Someone with a knack for surviving and someone who will clearly step up and help other people who need her even when she risks her own life.
That kind of person can be big trouble to a regime that's used to calling the shots. Better keep an eye on this one, Snow. She becomes even more defiant in the face of authority, and learns to play the media game to keep herself alive. The Capitol even becomes involved in making her out to be bigger than she is, starting with the "Girl on Fire" moniker.
The hype gets kicked into overdrive with the alleged romance with Peeta (still kinda sorta a story to feed the media instead of anything real). Finally, Snow picks up on the possibility that she may be a threat and, in pushing it, actually makes her even harder to kill:
SNOW: An eleven?
SENECA: She earned it.
SNOW: She shot an arrow at your head.
SENECA: Well, at an apple.
SNOW: Near your head.
Katniss is just a little spark right now. But that spark is a heck of a lot bigger by the end of the Games, setting the stage for the heroine she'll eventually become.
But that's a story for another movie.