If you just want to dual boot between OS X 10.9 Mavericks and Mac OS X 10.6 Snow Leopard (which has to run on 2011 or older hardware, 2012 and newer hardware will not work), create a second partition via Disk Utility and boot from the Mac OS X 10.6 Snow Leopard installer and install Mac OS X 10.6 Snow Leopard onto that new partition.
If you also want to use Windows then, you have to look further, probably. rEFIt might help.