Some samples:

1. Extended Cougar Walk
Group of students and fans start at the Provo library (old BYA. Has a Brigham statue out front.) Have mini pep rally, perhaps include that game's flag bearers. Flag bearers and fans walk together up the southwest stairs, all the way across campus and to the stadium gathering people as they go. Then create the tunnel through which our team walks
2. Yell Practice
Idea stolen from Texas A&M. Basically get together the night before the game and have cheerleaders teach unified, opponent specific cheers for each game. Heck, make it into a carnival. Have food, games...whatever.
3. Danites
Stolen from USC's Trojan knights. Can be like existing fan groups on campus, but more dedicated and fraternity like. Danites name may be controversial, but something like that.
4. Traffic solutions
Why University Ave doesn't have lights like 5400 south boggles my mind.