In chapter 2 of S.E. Hinton's Rumblefish Hinton uses the technique of foreshadowing to hint at what is going to happen in the story.
I was hanging out at Benny's, playing pool, when I heard Biff Wilcox was looking to kill me.
This sets the stage for what will happen later. We get the impression that their will be a fight between the two boys. Eventually they do.
The author uses the literary device tone or mood by creating a sense of seriousness. Rusty-James took the threat more serious after talking to Midget.