I bought a xenia frag yesterday and it wasn't attached to anything. I took a piece of rock from my tank and I used a rubber band to hold them together. Less than 24 hours later, SUCCESS!!! It has attached itself to the rock!!! Just got home from work and saw it. Pretty excited about it! Lol. =D
So anyway, the rubber band trick works great! Oh, and make sure the frag is sitting in a low flow area of the tank so it's not moving around too much and it attaches sooner.
I find attaching my corals a nightmare. My fish don't bother any established corals but the second something new is in they don't leave it alone until they've ripped it from the rocks. Little buggers