Do a google search, particularly an image search, for "atlatl", and see what comes up.  That will explain, probably, what I'm about to say.
  Get a piece of wood about as long as your forearm.  Carve a deep, wide, long groove in one end, and the other end will be the handle.  Make a dart about 6 feet long, and fletch it with feathers, like you would an arrow.  Give it a large, spear-like head.  Insert the end, not the tip, into the groove, and swing it forewards, completely 270 degrees, and there you go.  One atlatl.  Just google it dude.

www.atlatl.com is good too.  But googling it will bring up so many other sites.

here is a link to a book you could buy off of ebay that i am sure would help you.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7701503478&category=13764&ssP...