If you don't have access to one of the guitar-shaped controllers that come with the various releases of the "Guitar Hero" series, you can control the game and rock out using a regular PlayStation 3 DualShock controller. Although the experience won't be quite the same, all of the notes and activities you can perform on the guitar-shaped controller can easily be performed on the regular controller, as long as you know which buttons to press.
Use the "L2" and "L1" buttons to play "green" coloured notes and "red" coloured notes, respectively. The "L2" and "L1" buttons are the left shoulder buttons, located at the top of the DualShock controller.
Use the "R2" and "R1" buttons to play "blue" coloured notes and "yellow" coloured notes, respectively. The "R2" and "R1" buttons are the right shoulder buttons, located at the top of the DualShock controller.
Use the "X" button on the front of your DualShock controller to play "orange" coloured notes during songs.
Use the "Select" button to use the "Start Power" that you build up during songs. This can give you a bonus, causing you to win more points than normal during gameplay.
Use the "Left" joystick on the front of your DualShock controller to act as the "whammy bar." This bar can change the pitch of notes during gameplay, which can cause you to win more points--if used correctly.