Here's a few ideas, thinking out loud,
-No one will be attempting to 'study' at this expo. Offering live academic advice will be pointless. They want university info, careers and things of that like.
-We need to heavily advertise the ENTER calculator (especially the ENTER calculator, and possibly my SS estimator).
-Our selling point should be how resourceful the community can be, in the sense that we can help out with virtually every secondary-education related issue (and the fact that we have every resource that can be had, but probably should keep that low since all the major exam companies will be there).
-We should definitely have live registrations, and print out a bunch of business cards so they can take their new username and passwords with them.
-Need to sell the idea that we have many tertiary students at prestigious universities. We can offer course selection advice no other service can.
-DEFINITELY make a mailing list of new members. If all goes well, many will register on the day, but few will come back. Need to send them non-intrusive reminders with some kind of incentive to return, such as....
--'community events', like holding a SACs information week on the forums where mods give some insights into upcoming SACs (they are all pretty predictable), maybe run a tutorial of some kind, whatever
--Tertiary information week or something, and we spend a few more minutes answering uni-related questions, w/ever
That's about it from me for the moment. I don't know how well the expo will respond if runners are sent to cover more ground/audience with flyers (possibly against the rules). You probably want to start thinking about decorations now. Also, internet connection on the day.