Get tickets for that as soon as they become available.
If it's anything like the Toronto one (which, I assume it is), tickets go insanely fast. Even with a ticket, I still had to wait over an hour to get inside, plus another 30 half hour at the end to get a picture on the Iron Throne. They do have rush tickets available, but the line for that is always long, and then you'll be waiting in the same lines as people with tickets.