First, it depends on the type of coral. Most people (including myself) don't seem to have much luck getting soft corals to stick to anything using superglue. I had one person suggest using needle and thread and basically sewing it to a piece of rubble rock and then you can superglue or epoxy (or both) the rock where you want it. I've tried this with leathers and 'shrooms and it works great for me. I like Capt_Cully's method. It sounds like that should work great for stoney corals. I'll have to try that next time I get a frag. Along those lines, if you're attaching a stoney coral and you think you might move it later, I'd suggest one of two things. I'll usually try to find a crevice where I can wedge it in if it's something branchlike (candy cane frag for example) or a valley or larger crevice where it's not likely to fall off for a larger frag. If it seems happy there, I'll then attach it permanently. If you can't find a suitable place like that, go with a moderate amount of superglue. I've moved a couple superglued frags after the fact and it wasn't too difficult to pry them off. And if they seem happy where you put them, you can add epoxy to secure them more permanently.