The way in which Katniss finds herself in conflict with the Capitol and President Snow is something that develops as this gripping novel goes on. A key quote that you can use comes from Peeta in Chapter Ten, when he is talking with Katniss about how he wants to behave during the games:
Only I keep wishing I could think of a way to... to show the Capitol they don't own me. That I'm more than just a piece in their Games.
This is something that both Katniss and Peeta go on to demonstrate in their own performance during the Games. Note the way that Katniss weaves flowers into Rue's body as a direct slap in the face to the Capitol. Note what Katniss says about her aim:
I want to do something, right here, right now, to shame them, to make them accountable, to show the Capitol that whatever they do or force us to do there is a part of every tribute they can't own. That rue was more than a piece in their Games. And so am I.
Katniss, through such acts, deilberately places herself in conflict with the Capitol precisely because she refuses to be a simple "piece in their Games." This is an excellent example to use, as is the way that Peeta and Katniss force the Capitol to let them win the Games jointly.