When you go to play sweet child o mine(u must be on expert or will not work) and you need to be in co-op player 2 guitar has to be guitar and player 1 guitar has to be bass. About 4 notes through the intro to the song just start strumming and holding in the red button as fast as possible.......doing this lags the game and your meter wont go down and it will think you hit every note.......u can do anything during the song exceot hit the notes in the song or you will mess up the whole cheat.........me and my friend figured this out one day when we were bored.

At the main menu put your cursor bar thing on the quickplay option and press Blue orange yellow orange blue orange yellow yellow, I remember this easily by BOYOBOYY

Yellow, Blue, Yellow, Orange, Yellow, Blue

Do this at the start menu.