I know where to find some of the cards:
1: secret passage in Gryffindor tower (behind bookcase)
2&3: Secret passages in th Great Foyer (Bookcases)
4,5&6:Secret passages in the grounds (Behind Walls)
7,8&9: Secret Passages in the dungeons (Bookcases)
10: Secret Passage in the upper castle (Bookcase)
11: get all Knuts and gems in the Gringotts level
12: Get all Sickles and gems
13: Get all Galleons and gems
14: Forbidden Forest. at the start of the level turn around and cast Charged Flippendo at the wall
15:Dungeon: Get the kitten to Raymond
16: Behind the portrait in the grounds
I don't know where to find the last one but if you get it Ron will give you the eighteenth card (Harry Potter
We have more cheats and tips for this game here, Harry Potter and the Sorcerers Stone cheats
Comments for this hint