Well, you will need really good water quality of course so if you dont already have one, you need to get a test kit to test for ammonia, nitrite, nitrates, etc. I also recommend getting a refractometer for measuring the salinity if you dont already have one because they are much more accurate than a hydrometer and it is important to have good salinity with corals and fish as well.
You will also want good lights. Depending on what lights you have, you may be limited to certain corals. Metal halides are more expensive but they allow you to have most of the corals sold in this trade. OTher lights such as compact florescents and such can limit the types of corals that will do well in the aquarium...
You will also want to have biological filtration through live sand, live rock, and a clean up crew to help stabilize the system. Stability is key for corals!
As far as coral care, you may need to add supplements such as calcium to help hard corals build their skeleton and you also will need to feed corals. Some accept meaty foods while others eat phytoplankton.
Does that help?
