During gameplay, pause the game and enter the folloing codes:

Infinite Health
     Up, Up, Down, Down, Left, Right, Left, Right, L1, L1, R1, R1

Infinite Breath
     Up, Up, Down, Down, Left, Right, Left, Right, L1, R1, L1, R1 

EXTRAS: Elijah Wood Interview 
     Complete  the  game once to unlock the 'extras' menu at the title
screen. From here you can access an interview with Elijahh Wood.

New Game+ 
     After  you complete the game be sure to save. You will be able to
restart  the  game  with  all  the  stats  you had leveled up when you
completed the game.