We may learn later, through flashbacks, exposition, or inference, about events occurring before the beginning of the story. Any important character, location, or object should be foreshadowed early in the story. The trick is to put the plot element into your story without making the reader excessively aware of its importance. Chance and coincidence, in particular, require careful preparation if they are going to influence the plot. Keep in mind the kind of story you're telling.
Any story is about the relationship of an individual to society.
A comic story describes an isolated individual achieving social integration either by being accepted into an existing society or by forming his own. This integration is often symbolized by a wedding or feast. The plot should keep us in some degree of suspense about what kind of story we're reading. If we know the hero is doomed, his downfall should stem from a factor we know about but have not given sufficient weight to. Ironic plots subvert their surface meanings.