From Jack's mom spending so much time cooking meals for the elderly women of the town, to Jack's dad's destruction of property, the actions of the book's characters reveal a lot about their character and values. It doesn't take much to figure out that the Hells Angels are vicious brutes: just take a look at how they burn down Miss Volker's sister's house. Similarly, all we need to know about Jack's dad is that he dive-bombs abandoned houses to know that he hasn't quite grown up.
And when we see Bunny literally pushing Jack around to get her way? We know that she's a slightly obnoxious (though brave), strong-headed girl.
Speech and Dialogue
Dead End in Norvelt is full of talking, and Gantos uses dialogue to give us info on his characters. We learn a lot about people just by the words they use and the way they interact with each other..
For instance, we get a big clue that Mr. Spizz is a rude jerk by the way he always calls Jack "Gantos boy," without even bothering to use his real name. Miss Volker's fiery nature certainly blazes through in her strutting, active speeches. And Jack? Jack just tosses out an endless stream of questions. Curious, smart, and, yeah, a little insecure.