Katniss volunteers for her sister at the 74th annual reaping. This is heroic because katniss is risking her life to save her sisters because she knows she has a better chance than prim at winning.
Katniss puts her name in for the reaping again for some tessrae (oil and grain). This is heroic because Katniss is making the chance of her being killed bigger so that she can get extra supply's for her family. This is a selfless act.
As long as you wear this pin, nothing bad will happen to you.
Katniss goes to the capital to train before the games. When it is her time to show the "game makers' what she can do they don't pay attention to her so she shoots an arrow at them and hits the apple sitting in the pigs mouth. This is an example of katniss being a risk taker, she takes risks and stands up for herself when she was feeling ignored.
Promise Gale, you wont let them starve!
Katniss sneaks into the forest and collects plants and hunts for her sister and mom all the time even though it is against the rules. This is heroic because if she is caught by the game makers then she could be beat or even face death.
Katniss gives prim a pin that she got from a lady at the market and tell prim that as long as she wears it nothing bad will happen to her. Katniss is being selfless she is trying to help prim have hope that she wont get picked at the reaping.
Before katniss gets taken away to get on the train for the hunger games. she talks to gale. She tells gale to take care of her family and to bring them game. This is an example of a heroic act. Katniss is being selfless and instead of worrying about dying in the arena she is worrying about making sure her family survives.