What are the conflicts and choices that were made in the movie? Why?

The Hunger Games, both Suzanne Collins's novel and the film adaptation directed by Gary Ross, present life-or-death conflicts for the characters both before and during the Capitol's Hunger Games. Katniss, a young woman from District 12, is our protagonist. She grows up having to make tough choices because after her father dies, she must help provide for the family (her mother and her sister, Prim). She is a skilled hunter, but hunting is illegal and severely punishable; therefore, Katniss must choose her family's survival over the government's laws, and this is a conflict that we will see continue throughout the full Hunger Games series. 
Once the day for the Reaping arrives, Katniss and her fellow District 12 peers huddle into the center of town for the ceremony that will choose one girl and one boy from the District to participate in the Hunger Games. These brutal games pit two "tributes" from each district against each other in a fight to the death. Only one "victor" will come out alive. On the morning of the Reaping, Katniss's young sister, Prim, is concerned and nervous, though Katniss reassures her that, as Prim has only this year become eligible for the Games, she will most likely not be chosen. Of course, Katniss is wrong, and Prim's name is indeed drawn. Instinctively, Katniss volunteers for her sister and goes to the Games in her place. This is another painful choice for Katniss, but she feels she must protect Prim at any cost.
Once Katniss leaves District 12 to head to the Games, she must decide whether to trust Peeta, the boy from District 12, and her mentor, Haymitch, who is drunk and apathetic. Eventually, all three do bond, but Katniss and Haymitch butt heads many times. Haymitch, though, is proud of Katniss and believes in her ability.
When the Games begin, the characters must decide how to "play the game": hide out and hope for the best or attack and kill as many competitors as possible. Katniss chooses to run for a backpack with supplies and then head to the woods. When she and Foxface run into each other on the way to the forest, she can choose to kill Foxface, but they just exchange a long stare and go their separate ways. Katniss is not prepared to kill other tributes yet. Later, she must do what she needs to do to survive. When she is chased up a tree by the "careers," she decides, with the help of Rue, to drop a hive on the sleeping careers below, and one of them is killed, while the others are injured. Katniss chooses to form a bond with Rue, who reminds her of Prim, and when Rue is tragically killed, Katniss decides to show her love for Rue publicly, despite the Government's obvious disapproval. She thus earns the loyalty of the people from Rue's district and the game's other tribute from Rue's district, who later saves Katniss's life when Clove tries to kill her.
Ultimately, Katniss also decides to risk her life to help Peeta, whom she was not sure was even on her side for a while (he was with the careers earlier in the Games). The two form an extremely strong bond and even go as far as to try to commit suicide together at the end of the Games, so one does not have to kill the other. They are subsequently named co-victors, but they will face consequences in the books / films that follow.
The Hunger Games presents all of the characters, but especially Katniss, with a series of choices; many of the scenarios really have no good "solutions," but Katniss must weigh the risks and benefits of each decision. We learn from The Hunger Games that Katniss is fiercely loyal to family and friends and will openly defy the Capitol and President Snow to protect those she loves.