I would suggest that you do some caching for a while, attend some Events and talk to folks there... I bet all (almost) your questions will be answered just by playing.
On the other hand you may be interested also in some geocaching based books and movies or series, like Splinterheads, Dark, etc.
Some rare geocoins would be good things to leave in the caches, or memorabilia from pop culture, like the original artifacts in the APE Cache series, from Planet of the Apes.
Enjoy and be inspired.
PS: I have done a lot of covers for the portuguese versions of Goosebumps, from R. L. Stine.