Insert the spoon between the tines of the fork and balance the system on the edge of the glass using a toothpick.
For extra fun: Burn the toothpick from the inside end, and ask the students when the system will fall. IT WON'T! The flame goes out when it gets to the edge of the glass and the heat is absorbed by the glass. The fork and spoon remain balanced. Check out the video below of this in action.