Why do you think George asks Lennie to familiarize himself with the location of the clearing where they spend the night?

If Lennie happens to get into any trouble, George wants him to run away and hide at the clearing. They have just come from a job in Weed. They had to leave because Lennie felt a girl's dress and panicked when she tried to get away from him. Lennie ended up hanging on to her dress, which the girl took as a sign of aggression.
George adds, "She yells and we got to hide in a irrigation ditch all day with guys lookin' for us, and we got to sneak out in the dark and get outa the country." Lennie can't help himself when it comes to soft things like rabbits, puppies, and girls. He also doesn't know his own strength. Lennie is innocent but destructive.
George knows the possibility exists that Lennie might cause some trouble again. Near the end of the chapter, George tells Lennie to come back to the clearing and hide in the brush.

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 is certainly a bit of foreshadowing, even though George tries to convince Lennie that this time will be different.