A great place to start when looking for different corals is here:
http://www.reefcorner.com/specimen_Sheets.htm">http://www.reefcorner.com/specimen_Sheets.htm</a>
You can look at different corals and care specs for each. Be weary about impulse buys, do your research and then go find the best specimen you can find. As for health, look at overall color, skin/tissue, and polyp extension. And remember that even though a coral may be brown, doesn't mean its not healthy. I have had many a SPS or zoas that was brown at first and morphed into a beautiful specimen.