All this is shown primarily through first-person narration in the novel -- the only way they could do the same in movies is via voiceovers, which the movie happily avoids, since it's invariably terrible. Jennifer Lawrence does a fantastic job conveying Kayniss' thoughts and feelings silently, but she's still limited into how much information/character she can convey by the medium. She's the best movie Katniss we could possibly have, and likewise, the movie is pretty much the best adaptation of the book we could likely get -- but the movie's strengths are primarily the book's, and the book is just stronger overall. Some assorted thoughts:
• The Hunger Games movie is two and a half hours long and just flies by; it still has to drop some bits, but nothing so integral as to cause a fan uproar.
• I was worried that the movie would play up the non-existent love triangle in order to bring in the Twilight fans, but they kept it exactly in the book -- her relationship with Gale is unspoken and unrealized before Katniss is whisked off to the Games, and her "relationship" with Peeta is a survival tactic first and foremost, even if Peeta actually means it. These two boys may be deeply in love with Katniss, but they don't spend their time taking off their shirts and strutting for her, and even if they did, Katniss has much more on her mind than boys -- specifically surviving.
• I didn't like the guys who played Gale or Peeta very much at first, but Peeta grew on me... exactly like he did in the book. I'd say that counts for something. Gale is just a slab of generic boy actor, but his character gets more defined in the later books, so I'll holding off judging the actor until then.
• I can't decide if Leny Kravitz's performance as Cinna was understated or actually kind of crappy. Honestly, I can't tell. All the other supporting actors were great, though. That girl who played Rue was very good.
• Speaking of, if you're one of the people who was actually upset to discover Rue was black in the movie, you are a terrible reader and a worse person. Case closed.
• I really liked the Capitol's white thug uniforms. They look like what soldiers in post-apocalyptic fascist dicatatorships were in '80s Italian flick. The simplicity worked for me.
• My biggest problem with the movie, in all honesty? Katniss' "fire" dress. That sucked. Guys, you knew this movie was going to make a billion dollars -- couldn't you have ponied up a but more for the CG here?
All said, I do recommend seeing the movie -- but I wholeheartedly recommend reading the book more.