Just outside the great hall, use dark magic on the object to the right of the owl.
Enter the divination room and assemble the box on the right side. Use this box to get up to the Spectrespecs, then assemble the invisible object on the left side of the room. Break open the newly formed crystal ball to find the red brick.
On the streets of Hogsmead. Grab the Spectrespecs nearby and use them to reassemble a snowman in the lower left corner of the screen.
At the train station, look for the red lock. You need Diffindo to break it open.
On the path to Hogsmeade, use Ron’s Deluminator to take the light from next to the owl all the way over to the lamp on the right.
Along the path between Hogwarts and the train station, use Hermione’s bag in the spot pictured above.
Outside the castle, take the forest path towards the bottom of the screen to find a gate. Use Hermione’s bag to open it up, then in the next area, use Reducto on the statue.
Allows you to collect ghost studs, which are dropped by the guide and worth 1,000 each. In this small courtyard, use Diffindo on the tree. This frees up a red brick, which you can carry over to the owl to unlock the brick.