Ain't no fun in shooting a bow you had to buy. Not like shooting a bow you MAKE!
Start looking for an osage tree with no limbs for the first 7 feet or so. Look at the grain of the bark. Follow the valleys of the bark as you look from the base of the tree and upwards. Does the bark seem to twist around the tree? If so, walk on and find another. If the bark seems to run straight up and down the tree then it is likely to split along those lines! Mark this tree in your mind and run for a chain saw!
Or better yet, hang around in here a little bit and meet some of the Iowa bowyers and offer to go out woodcutting with them. Who knows, they may trade you a seasoned stave for your efforts!