Well, yes, but that's far too open-ended of a question to get a response containing 'what you need to know'.
Start by reading Robert Fenner's The Conscientious Marine Aquarist. After that, you should be ready to start buying equipment.
Biggest thing: this is a slow, very patient, some what expensive hobby...so don't rush ANYTHING.
Former advisor and planted tank geek...life's moved on though.