You can usually find good advice on placement for specific corals here on R2R, as well as on the Tidal Gardens website. Keep in mind, it is not just about placement as it relates to light, but also placement as it relates to flow.
Also some corals can be atypical compared to the generally accpeted placment parametrs of their own species.
Case in point, my Indigo Discosoma Mushroom. Normally, advice for all types of Mushroom Corals is to place them in lower light towards the bottom of a tank in low flow. Emphasis: NORMALLY. Not my Indigo, though. It hated it towards the bottom. I wound up moving to the highest point of my tank, directly below the light, and from what I can tell the flow is notmally higher up at the top than at the bottom due to how my return nozzle is situated (pointing up towards the surface of the water). It took less than an hour for the Indigo to being all shriveled up and unhappy to spread out and quite obviously happy. A month later it doubled in size. Nowadays it fully opens to about 3.5inches in diameter, and also had itself a baby!!
But, I have noticed that usually the advice on coral placement tends to be correct.
Any specifc corals you considering placement for?