We raised night crawlers in a thing commonly called a compost pile. If starting from scratch add some lime, water, and turn the leaves and grass clippings over once a month to help it break down quicker and you should have a great bed in a year. You can speed things up a bit by laying down a couple inches of top soil, peat, and compost first and adding a couple dozen night crawlers to this layer. The worms will break down the leaves and clippings all by themselves. Adding food stuffs attracts raccoons, skunks, opossums, and the like which cause other problems in addition to eating the worms.
I have taken a couple thousand night crawlers out of an 8'x8'x3' compost pile at one time and still had plenty for the next couple months. This is the best way to ranch them as it takes little effort. One can remove 3/4 of the compost early in the year and use it for gardens. Just fill the pile up by fall so there will be plenty for the worms to winter in by fall.
