I would be there 20 minutes or so before official opening but then I am a Rope Drop everytime tourer when at WDW so being at the park for opening is my normal mode. I don't think it is quite as important at SW but the same basics are fighting you as at WDW earlier equals good to best parking opportunity if you are driving to SW (it is a huge parking lot natuarally and you can end up "way over there" and far from the turnstiles arriving later but tehy have a tram in the lot and it is pretty efficient. Customer service office (annual passes, upgrades special needs etc and the ticket booths usually open 15 to 30 minutes before the parks and at peak seasons I have seen them do a soft opening of the stores and restaurant (there is a pretty decent little shop with pastrys and grab and go breakfast items near the entrance). there will be a Shanu character inetraction opportunity at Rope Drop and the early sting-ray feeding is within 15 minutes or so after the official park opening. The rides will build lines as teh day goes on and timing things for while "everyone else" is seeing Shamu or teh Ski show or whatever is easier if you already saw them at teh first show of the day.
Small children to tween-agers will love Shamus Happy Harbour
The daytime Shamu show is completely different from the night time version so if you are on a single day touring plan that is important to factor in to your plans i.e see both.
The stadiums are all pretty good size so it is basically a get there a few miutes ahead of time and leave in the with the masses experience the trick is getting the events near Shamu done during a different show so you are joining the long lines that form afterwards.