There may be a lot of words thrown around in this book, but actions definitely speak louder than words for all of our favorite characters. We learn about Claudia and Jamie through their actions. They're brave; after all, they both decide to run away from home and manage to navigate things like feeding themselves and getting around New York City by themselves. Most adult tourists couldn't even handle that much.
We know that Claudia is a perfectionist because she gets terribly upset when things don't go her way (take a look at when she receives that letter from museum officials, for example). And we know that Jamie is a quick thinker because he manages to escape from the bathroom when the janitor finds him in there and asks him where he came from.
We learn quite a bit about the more peripheral characters from their actions as well. Even though Mrs. Frankweiler talks like she's a cranky, difficult old woman, she still takes the children into her home, feeds them, and hands over the secret they've been searching for. She's a total softie when it comes down to it.
We even get a little sense of Claudia and Jamie's parents from their actions. We know that they're worried about the kids, and that they phone Mrs. Frankweiler to ask lots of questions. They're real, concerned parents, even if we don't see much of them in the book.
We can look as far as the text for some insight into the characters. Like a particularly honest friend, sometimes the book just comes out and says what the characters are like, whether it's flattering or not.
When we meet Claudia, she's described in the following way: "She didn't like discomfort; even picnics were untidy and inconvenient: all those insects and the sun melting the icing on the cupcakes" (1.1). This certainly gives the reader a sense of what Claudia is like: she has high standards, is picky, and can be a little prissy. As for Jamie, he tells us outright what he's like, stating, "I like complications" (1.58).
There's no tiptoeing around the issue when it comes to describing the book's main duo. We know some of their personality traits right off the bat. And hey, it's always good to know what you're getting into when you pick up a book.
There's a whole lot of talking that goes on between the characters in this book—none of them can really seem to keep their mouths shut. It's good for the reader, though, because we get to see how their interactions work and what that tells us about the characters. Take this exchange between Jamie and Claudia at the beginning of the book:
"Do I have to eat it?" Jamie asked.
"Tearing it up and putting it in the trash would be much simpler. No one in our family but me ever goes through the trash. And I only do if it is not sloppy and not full of pencil sharpener shavings. Or ashes."
"I'll eat it. I like complications," Jamie said.
"You must also like wood pulp," Claudia said. "That's what paper is made of, you know." (1.57-60)
It's a short passage, but it tells us a lot of what we need to know about these kids. Claudia is pretty matter-of-fact and plans things out far in advance. She also doesn't like messy things (like the sloppy trash) and likes to show off her knowledge; she has to say that paper is made out of wood pulp, even though it's not really relevant.
As for Jamie, we find out that he likes complications, and that he also has this movie-inspired version of how he thinks running away will be. Later on, we'll learn about how he carries a compass and thinks that real running away involves camping out in Central Park. But for now, we get the first hint of that when he suggests that he should eat the paper. What is this, a spy flick?