I have found fossils, mineral specimens, Indian artifacts, century old bottles, a few coins, and some gem material (and on drilling rigs, quite a bit of oil).
The trick is to not prejudice yourself, and see what there is, rather than look for one thing and end up ignoring others.
Sometimes, the treasure is in the looking, not the finding--if nothing else, the experience is pretty neat.
Well said. So many people walk the same spot and only the guy with the open mind sees it.