If your swapping lighting systems, i'd start at the lowest settings and probably slowly increase the lighting about once or twice a week until you reach your goal. If your talking about a new coral bought from a LFS, i like to put the corals at the edges of my tank and slowly move them towards the center for a week or two, and then I put them in their final position. Some people like to shade the corals and slowly move them into the light as well.
