Best way to beat USC is to follow Notre Dame's plan earlier this year. Dink and Dunk, run the ball, and (the main thing) keep USC's offense off the field.
ND had the ball for 30 plus minutes in the game, USC was around 20 minutes, and lest we forget, it took Reggie Bush pushing Leinart across the goal line for USC to win. Oh, and ND blowing two golden chances in the middle of the game.
That was W Va's strategy in their bowl (I think it was anyway) and they beat GA.... GA scored at will when they did have the ball.