I want to only put in those rare corals and things and have a true 'Dream Tank'. I really need help in this area and would like some guidance from you guys sinse I dont know what is or is not rare.
Welcome to the dark side
. First off, in my opinion if your really going to do this, you will need to let the new tank mature for at least 6 months, have a very good skimmer, good lighting, very stable parameters, and a light fish load. There will be nothing more disheartening than dropping $500 worth of pencil eraser head sized coral into a new tank and watching them disappear. Most of these frags are very small and need very good water quality to survive.
Easiest way to tell a real rare coral - rare = $$$$$$, hard to get without shipping, and frags about this size - O.
Ok, maybe a little larger but 1/4 x 1/4 is not unusual. You may ask why the rare stuff? My experience is that it holds its color and is true to a photo of it. A real original Superman montipora is a baby blue skin with bright orange/red polyps. Not a medium blue with dull brownish red polyps that was out there a few years back.
Ask when you see something that catches your eye. There are more than a few of us that can give you some info on it.