Well there's several good threads here about starting saltwater. Cycling is pretty much the same process (the bacteria is different though, so what cycles a fresh tank won't cycle a salt tank) just like fresh, certain fish cannot be kept together. Salt requires monitoring of the salinity, and added freshwater to replace what evaporates. The fish, some say, can be more delicate. There are also some pretty good books on "your first marine aquarium", check amazon for the best prices.
125 malawi cichlid, 110 Discus, 75 reef, 30 reef, 27 reef, 4 planted