Since Steinbeck relies heavily on dialogue in this work, it is easy to find dialogue that foreshadows future plot developments.
In the first chapter, George tells Lennie to look around the place where they are camping overnight and remember it. Then he says:
"Well, look. Lennie--if you jus' happen to get in trouble like you always done before, I want you to come right here an' hide in the brush."
This foreshadows what will happen in the fifth and sixth chapters. Lennie will accidentally kill Curley's wife in the barn and remember that George told him precisely what to do if he got into trouble. George will know where Lennie is hiding and be able to find him before the fugitive is located by any of the other men who are hunting him down.
In the second chapter Curley enters the bunkhouse and has a brief confrontation with Lennie, then leaves. George asks Candy:
"What's he got against Lennie?"
The swamper considered. . . . "Well, . . . tell you what. Curley's like a lot of little guys. He hates big guys. He's alla time picking scraps with big guys. Kind of like he's mad at 'em because he ain't a big guy. You seen little guys like that, ain't you? Always scrappy?"
"Lennie ain't handy, but this Curley punk is gonna get hurt if he messes around with Lennie."
This foreshadows the scene in which Curley starts punching Lennie without any reasonable provocation and Lennie crushes Curley's hand. The reader expects to see some such fight occur sooner or later, and this lends dramatic tension to the story. The fight demonstrates Lennie's tremendous strength, so that it is easy to understand how he could break Curley's wife's neck by accident.
Steinbeck was good at writing dialogue. His dialogue not only furnishes information to the reader but provides dramatic suspense by foreshadowiing future events and is also of great importance in characterizing and differentiating the individuals in his cast.