I get all of my ripstop from Hancock Fabrics - it is the cheapest place in town and they have a better selection than Jo Ann Fabrics. Once in a while a Fabric Outlet here will have a 1/2 off sale and then that is cheaper than Hancock - but not much.
The best way is with a hot knife - it's a tool that is like a soldering iron and it seals it from fraying. I don't have one and haven't had any interest in it. The next best way for me is a rotary cutter Makes clean edges. For getting a good edge a serger machine is very nice.