Generally, the best thing to do is to get frozen pre-killed mice, thaw them under a heatlamp, and dangle them with a pair of LONG tweezers or a pair of hemostats in front of the snake....AKA "the mousie dance". Make sure the prey's warm enough, or the snake may not take it. I usually have to make my f/t rats dance around for quite a bit before Roo will take them. You can buy mice and pre-kill them, but that's just in general a bigger pain in the butt, and takes a much stronger stomach.
Also, be careful not to get them wet when thawing, the snake may not take it if it doesn't smell like prey.
Good luck!