Make sure to move your corals, clams, etc to the bottom of the tank during the acclimation period. You'll be less likely to fry them. When I switched from VHOs to MHs, I fried a lot of the soft corals that were near the top of my tank.
Edit: I started at 5 hours and worked my way up to 10 hours over a couple of months. If I had kept all my corals near the bottom of the tank, I wouldn't have lost any of them.