A few suggestions:
1) I've been sitting in the student section for a long time and the biggest issue we have right now outside of not being a great team is the Jumbotron. Everything from the games, music, videos, etc has killed the atmostphere in the stadium. Things like a non enthusiastic dawg pound rock do mattter and should be addressed.
2) All frats should force the pledges to stay the entire game.
3) No gimmicks are going to keep students there. It comes down to psycology and making the stadium feel like "the place to be". Pay a DJ and marketing guru to find out the exact timing and what songs to play along with what a college age student or recruit would find fun and do it. It's not that difficult. One example of this is playing the "Bring em out, Bring em out" song when the team comes on the field. An energy is immediately created when that happens but we have to consistently do this throughout the entire game.

**The problem with blocking off seats is that it would create a late arriving crowd which is not what we want either.