Officially shut tailgating down 30 minutes before kickoff and close the gates to leave but still allow access to enter. There really is a sad large amount of fans that end up just going out there to drink, showing up late throughout the first quarter or not even making it into the stadium. Tell people to pack it up and either head to the entrance or exit. I absolutely LOVE the idea of the Bell ringing to say that "It's Football Time" and not "drinking time".
Lastly, you gotta get more students through the door. 1/4 off beers with current student ID? Kick for Cash every game? I think a cool and relatively easy way to get them to the stadium is Free Gameday parking at the Parking Towers with buses that will bring them to/from the stadium.