gangrel441:
This brings up an interesting question that you may be in a rather unique position to answer. If we come across a piece of hard coral that has been recently broken off and is still alive, but has fallen into a heavily sanded area between coral heads and is mostly shaded, would it do any good to reposition this piece so it would have a better chance to survive and form a new colony? If so, how would you recommend repositioning it? On a dead part of the reef, perhaps, or sanding up from the sand, etc..
There's been a lot of good discussion already as to whether this is a good idea or not. But if you're in a position of trying to get a fragment to survive, what do you do? They keys to survival are orientation, light, current, and food.
There's a definite right-side-up or upside-down, though it may not be obvious to untrained eyes. The feeding polyps are probably only on one side, as well as areas capable of growth and compensation for bright light. So figure out which way is up before planting that coral.
For many corals, light is critical. But it's not necessarily as much light as possible, but the right amount of light for that particular individual of that species. Too much light causes sunburn and possibly death. Too little light can starve a phototrophic coral. Over time an individual can adapt to a range of light levels, though there are always extremes. Orange cup corals prefer a dark cave; brain corals prefer direct sun. Being smothered in sand will likely kill any coral.
The right amount of current is also important. Stagnant water has less dissolved oxygen and little opportunity for filter feeders. High current can damage fragile structures or make it impossible for filter feeders to consume what they've caught. Again, the right amount of current depends on the species and individual.
Finally, there must be feeding opportunities where the coral resides. Some corals just need light, others just filter tiny particulates, or capture small creatures. Many use a combination of strategies.
So there are a lot of variables, more than you're likely to know. However, there's an easy way to cheat: look for the parent colony that this piece broke off of, and find a similar position. But keep in mind that if you stick that coral fragment into a hole in the reef, you may have just doomed the small fish that was living in that hole, and the still tiny genetically more diverse corals that had settled on that rock as a result of sexual reproduction.
Around a healthy reef, I wouldn't bother with this, as there is intense competition and helping one creature to survive is dooming another. On the other hand, in an area in decline or ravaged by hurricane, a little help isn't a bad thing.
-Mark