When the author gives out warnings and/or clues to indicate whats about to happen.
Foreshadoing in "Of Mice And Men"
An example from the book is when George says "Well look Lennie is you just happen to get in trouble like you always done before, I want you to come right here and hide behind the brush." Meaning that he knows that Lennie more likely to get into trouble again.
Another example I found was when George said to Lennie "I seen 'em poison before, but never seen no piece of jail bait worse than her." George is telling Lennie to stay away from Curly's wife because he knows she trouble and will cause trouble later on with Lennie, knowing how Lennie was looking at her for the first time.