It is best to go to the Sea World site and reference the day you are going. The day within the month park hours will contain the list of shows schedule for that day. http://www.seaworld.com/ParkHours.aspx?locID=1
I would note the show schedule may change, so it is best to check it prior to your departure.
Most shows are 30 minutes. Some shows are offered only a few times a day and some overlap, so it pays to do a little planning, especially if you are doing SW in one day. In your plan do not forget the travel times and getting there 15-30 minutes in advance..depending on where and how close you want to be to the stage/water.
Doing this in advance will make your experience a little more relaxed, in comparision to either winging it or trying to make a quick plan once you enter the park.
I dont think you really need an Itinerary for sea world. I believe once you have entered the park what you need to do is plan around the show times so for example: Shamu's Believe starts at 2:30pm for example, so what you could do you can do the animal exhibits or even the attractions so this would include: Shamu's Happy Harbour or the wild artic. Then once it gets to half an hour before the show then you can go to shamu stadium and wait for the show to start. So this is my idea.
I have read other poss that it is a good idea to either get to the coasters ASAP upon opening or go do the dolphin feeding if rides are not your thing.