There are some pretty good articles on this in the reefcentral mag. Basically all that is really required is some adhesive and something to mount it on, a piece of live rock rubble is what I usually use, though disks etc. may be more convenient. Super glue gel (not the runny liquid) works fine. Dry the base of the frag and the rock/disk with a paper towel, apply enough superglue to the rock to secure it, hold the two together for a minute or so and return to the tank. Don't go overboard with the glue, the frag has to encrust over the glue and the tissue that is covered in glue will die (unavoidable). Just use as much as is necessary. The glue cures almost instantly when it touches water, but I don't think the bond is as strong as when its allowed to dry in the air for a minute first before dunking. Larger pieces/colonies may require more elaborate strategies, but this method has worked for me for 1-2" frags.