One of the major themes in Of Mice and Men is the quest for the American Dream. George and Lennie, along with Candy and briefly Crooks share the quintessential dream of owning "a little piece of land." Throughout American history the goal of owning one's own land and having both freedom and security has been part of the Dream.
Unfortunately for the characters in the novel their dreams of ownership are never fulfilled. Although George, Lennie and Candy are poised to capture their dream, Lennie's killing of Curley's wife destroys their plans.
Here's an example of a paragraph using the Jane Shaffer model that should help:
As the title of his novel suggests, Steinbeck, from the outset, sets up his characters for failure in the quest to own a piece of land and realize their American Dream. The lines (from the Robert Burns poem "To a Mouse,") "the best laid plans of mice and men often go astray" directly relate to the final outcome of the novel. Even though George, Lennie and Candy are dreaming of the day when they can quit working for someone else and go live on their own farm we already know that these dreams are doomed. Steinbeck uses foreshadowing to show us that eventually Lennie will do "another bad thing" and disrupt their plans. Just as he did in Weed, Lennie is drawn to the shiny or the soft and he accidentally kills Curley's wife while stroking her hair. In chapter four, Crooks does a good job of summing up the idea that the dream can never be realized:
“You guys is just kiddin’ yourself. You’ll talk about it a hell of a lot, but you won’t get no land. You’ll be a swamper here till they take you out in a box. Hell, I seen too many guys. Lennie here’ll quit an’ be on the road in two, three weeks. Seems like ever’ guy got land in his head.”
Crooks is only partly right. Unfortunately for Lennie he loses not only his job but his life and George is unwilling to carry on with the dream without his friend. George says,
"I think I knowed from the very first. I think I know’d we’d never do her. He usta like to hear about it so much I got to thinking maybe we would.”
For Steinbeck the world in Of Mice and Men is a deterministic place and even though someone may have dreams they rarely come to fruition.