To get all the card decks from the beginning of the game, defeat Voldemort four times.
Getting rid of Peeves curse
When he sets the curse on you, go to the fifth or sixth floor and go to the upper left door. Go through a TV and battle. Once you win, you will get your present back.
Phantom conversation
When going to Snape's Potions Class, note that the Weasley Twins are still in the Common Room. Press Start and walk to where they where standing. Press A and you will be talking to them, even though they are not there.
Find rare Witches 'n Wizard cards
At platform 9 and 3 quarters go to the back of the last lamp post to the left and press A. It's a rare card every time!
117 Sicles
When you are playing go to the 4th floor and find the statue of the old man. Press A by him and you will get 117 Sicles.
