Before you set up a reef tank do some reading and ask questions at your local LFS. After you set up your tank ask questions at your local LFS or if you've found a website ask questions there. Reefkeeping is more than a hobby it becomes part of you and you'll want to be well informed of things to look for. Once you get to know your tank you'll develope a routine, just make you stick to it and do what works for you. As long as you do what is right for your tank you will always be happy with the results..
Learn all you can about one species of fish and one coral when starting out...especially a controversial one...like a blue tang...read, read, read. Then when you visit a LFS you can ask a question about that fish or coral. The information they give you will go a long way to finding out if they are trying to make a sale or if they are there to help you in the hobby.
FILTRATION, FILTRATION, FILTRATION. It doesn't have to be expensive to be good and cheap is usually just that. If you do not have a filtration sytem that will handle the load of main tank then there is no point in adding water let alone anything living.
Research before you get started and then continue to research afterwards. The more you know the more successful you will be. Ask questions and verify answers. Patience is the key as nothing fast is good.
Consistent maintenance of your equipment will save you money in lost fish, corals and time... not to mention the frustration when you find out your alk is 16 and your skimmer hasn't skimmed properly in three months.
Always research!!!!! I've been down the wrong road many times with my lfs considering hes out to make a sale, not help. Also, a handful of patience is better than a toilet full of fish. BE.PATIENT!
Saltwater and electricity are dangerous. Make sure that you prevent splashed or leaked water from getting into electronics by creating drip loops in your cords.