Great questions!! Am sure many others with much better advice will chime in on this thread. I will share what little I know to get things started...
1. As slow as you can, you are on the right track just by asking the question.
2. Sounds like a reef, so make sure you research everything! I love my LMB (lawn
mower blenny)and think everyone should have one.
3. Shrooms, shrooms and more shrooms. They are just so hardy. I dig the reds, blues, and the way my greens flouresce in my actnics.
4. Cleanup critters.
5. Snails will be part of your cleanupcrew, shrimp are part of the community.
6. LOTS!! A reeftank is full of preditation, surprises, and mystery. Is the ocean dangerous?
An anemone like aptasia can take over a tank killing anything in its way. A hitch-hikin' mantis hiding in your live rock could one day decide to dice up your new fish, or a
pistol shrimp that rode in starts crackin open your snails for dinner.
I had an emerald crab that thought hermit crabs were fun to rip apart. How about parasitic copepods that attach themselves to the outside of thier prey, gorging themselves on blood, before burrowing in to eat them alive from the inside-out? Had a bout with them, Believe you me that will creep ya out next time you shove your hand in the tank.