Here is a step by step picture tutorial on installing Windows 8 Release Preview on VMWare Player 4. Click on the images for a larger picture.
This is one of the easiest ways to test operating systems in general. I found that WMWare player works better than VirtualBox in some ways.
Windows 8 requires the user to hover in the lower left corner of the screen to launch the start screen, and I find it easier doing that on VMWare player than on VirtualBox because of WMWare player handles mouse movement.
Also, I encountered several problems with VirtualBox when resizing the VM window. Its just very clunky, and it freezes often. VMWare player on the other hand handles this a lot better.