If it hasn't become obvious to you, I love The Hunger Games. The whole trilogy. Everything. And upon watching the movie for the fourth time or so, something that bothered me finally clicked as to why it did.
In the book, right after Peeta's reaped, Katniss describes in detail how he saved her life by giving her bread and hope. In the movie, there's a brief flash of the two in the rain, but without context of what's actually going on.
Why does this bother me so much? Because in the book, we're given a strong characteristic as to who Peeta is. We see that he's kind and willing to sacrifice for others (his mom beats him because of what he did). Right away, the readers like Peeta, and the situation of the two going into the games gets more complicated.
In the movie, we get none of that. He's just a boy Katniss will have to fight against. Of course, those who read the books know about the bread, but those who haven't don't care. There's no emotion or connection between the two, and it takes a while to see Peeta's goodness come through the movie. And by then, most people will already have their feelings about him sorted.
This made me think of how important it is for us as writers to set up our character's personalities sooner rather than later. We can make the reader love (or hate, depending) the character with even a sentence, and hopefully within a scene. The bland characters, without their good or bad qualities coming through immediately, won't grasp the reader and then they won't care.
Sure, there are characters you can grow to love/hate, but the sooner the connection the reader has to them, the better. The sooner they'll think to themselves One more page, and get sucked in.
What do you do to make a reader instantly have an emotional reaction to your characters?