We always made up a treasure map, singed the edges and added some ketchup, and then stuffed it into an old bottle. There would be various "stations" that had to be found, with detailed instructions/puzzles at each one on how to find the next station. At the final station was a buried box stuffed with foil-wrapped chocolate coins. Sometimes a compass was required, and advice on how to "pace" a distance. It also helps if someone is familar with local landmarks, like "where the well-house used to be."

This may be hard to do in suburbia, but we sometimes did the same thing inside a building.

Cheerily,
Charley Noble