Legally you can't unless you have Apple hardware.
That said, a lot of people ignore the license and install it on non-Apple hardware, osx86project.org will be your best source of information.
Technically apple dont use apple harware either. The onlything Apple about a Apple is the sticker, and if you buy snow Leopard you get the same sticker. Slap it on and you just as apple as a real apple.