Depending on the type of lights you are running and the amount of lights will need to be factored in as well as how deep your tank is.
I know nothing is easy..
You definitely have to take those into acount.
I use Liveaquaria.com as a general guide.
They provide information such as below for each coral:
DFS Green People Eaters Zoanthus IM (Zoanthus gigantus)
Care Level: Easy
Temperament: Semi-aggressive
Lighting: Moderate
Waterflow: Medium
Placement: Bottom to Middle
Water Conditions: 72-78° F, dKH 8-12, sg 1.023-1.025, pH 8.0-8.4
Supplements: Iodine, Trace Elements
Compatibility: View Chart
Again, this is not a "bible" if you will, but it gives a beginner like me a place to start.
So if I was buying this type of coral, I see it should have moderate lighting, medium waterflow and should be placed bottom to middle of my tank.
If there is coral you want to know and cannot find it on their site, I google the name of the coral and placement.
So in google I would type in something like:
Green People Eaters Zoanthus placement
You should have a few threads to look at that contain the information you are looking for.
As grcforce above me posted, liveaquaria gives you information on stuff like that as well.
Here is what it says for a Hammer Coral:
It is moderately difficult to maintain, but with proper water conditions in the aquarium, it will thrive. It will require moderate lighting combined with moderate water movement within the aquarium. At night, its sweeper tentacles can extend up to six inches in the reef aquarium, stinging other species of corals and animals. Allow plenty of room between it and other neighboring corals. For continued good health, it will also require the addition of calcium, strontium, and other trace elements to the water.