After you leave the bonus bean room you fall into a series of very linear events. You need to just follow the Weasley brother. Along the way you will get the Marauder’s Map and run into McGonagall & Dumbledore before you reach the store. In the store feel free to look around. When you leave turn right and you’ll bump into Peeves. He has a list of passwords you want so you must cast him. If he gets a chance to throw something at you run toward him while holding the spell and it should go over you. Hold the left button long enough that Ron joins in. Once he’s defeated and you get the list you’re lead to meet Hermione in the Portrait Room.

Hogwarts Grounds

You’ll meet Neville here and want to follow him. The game will auto save along the way and you’ll be outside. Go straight across the yard toward Neville. At the entrance of class, you can choose to attack a pixie infestation on the left or go right into class.

Harry Potter and the Prisoner of Azkaban Walkthrough