All spells: After succesfully completeing the game, use the card combination that Dumbledore gave to you in the first battle you encounter. It will give you every spell for you to use for all future battles.
More Herbs: Stand in front of a piece of grass where you get herbs. Pick it up, go into your menu and exit out. More herbs will appear there.
Quick items from bushes: You can get items from the strange bushes quickly. Press A, then enter the start menu. Exit the menu, press A and anothert item will appear.
Incendo: To get Incendo, go to Professor McGonagall's classroom on the first floor and catch the rabbit.