How to set up a treasure map?

[zimmah]

one way to give people more chance and to avoid someone cracking it near instantly (and also give more people a chance of participating) is by giving several hints at several times.

for example one hint every week.

[tholenst]

I'm imagining a series of clues (think National Treasure), but not too obvious. If it's to be a world-wide hunt, it must therefore be difficult to crack. I don't want to hide the private key on a website or anything, but rather have the pieces be freely found in the public. So perhaps

Code:

E9

could represent the 233rd page of some book and so on.

Would love feedback and ideas.

Why not ask in a geocaching forum? They are experts in creating treasure hunts.