Sounds like a treasure hunt, right? Actually, going with the whole clue based nature of a treasure map, I'm going to talk about mysteries today. More specifically, how to go about creating a mystery that works. The process is really pretty simple.
First of all, you need to think of the mystery that is going to be solved. The best way to create a mystery story is to work your way from solved to the very first clue, moving backwards the whole way. Not necessary writing the whole story from the end to the beginning (wow, that would be interesting and complicated at the same time!), but figuring out what you want to be solved and the clues that are involved and working backward until your characters are getting ready to start everything.
Vague is the name of the game with mystery. You want your readers to discover everything with your characters so showing is essential. If you tell at any point, you'll ruin the whole experience. It also requires the ability to give very vivid descriptions.
One more element that is almost central to mystery stories is the element of danger. Of course, that danger isn't always a known danger, so you can expect to have (sorry for the acme reference here) anvils dropping from the ceiling often.
I applaud anyone who writes mystery novels for something I have been unable to accomplish. I aspire to be more like those amazing people every day.