sigh... as with any other worthwhile thing, you have to find a teacher. You can begin with the question: "what is zazen?" and the you can continue with the question: "what is zazen?"
Aren't you likely to get a knock to the noggin for asking such questions? My Iaido instructor told us to beware those bald guys in the robes. He said they were dangerous. This may have something to do with the fact that his sensei is a Zen monk. He's also the monk that performed my marriage.