I bought my first corals online then discovered my relatively local fish store specialist that has more corals in stock than this and most other online stores and for better or equal prices. here's a quote from their website "We have two coral system consisting of 17+ tanks holding approximatly 500+ corals. New arrivals weekly, stop by and check it out!!" I have no further use for online coral shopping now. Dont have to guess about the size, health or condition.
As far as advice, I would say go for the cheap and hardy corals online. the more difficult and expensive ones you'll want to inspect personally for damage and health. same goes for the ones known not to ship well.