Il n'y a pas vraiment de lieux secrets, mais je vais te donner la liste complète au cas où.
Walk With Luna
1-3. In the beginning of the game you walk straight passed these.
Quidditch Locker Room
1. On pedestal straight ahead.
Quidditch Tower
1. High on the tower on the right with the Hufflepuff flags.
2. On the staircase to the Training Grounds, behind the bench.
Training Grounds
1. At the top of the steps from the Quidditch Stadium, turn right. It's inside a plant.
2. From the Hufflepuff Dueling board, head around the outside of the fence.
3. Covered by plant on the wall to the left of the Herbology entrance.
4. From previous crest, walk along the wall towards Herbology and climb up the small stairs.
5. In the gate to the left of the Herbology entrance - break the pieces then levitate through the gate, repair
6. Same as previous, but to the right
7. From previous Crest, walk to the right until you come to a doorway with a vase inside. Crest is above the doorway.
8. From previous Crest, walk along the wall and around to the right. Crest is inside spiderwebs
9. On a rock just outside the Herbology entrance.
Herbology
1. Upon entering from Training Grounds, turn around and check above and to left of the door.
2. Head into the greenhouse on the left. Use Wingardium Leviosa in the corner to your left.
3. In the greenhouse with Potions Club, head all the way to the back room.
4. Straight back between the two greenhouses, next to a box of dung bombs. You will need to repair it.
5. Head to the door that leads to the Transfiguration Corridor. Go through it, and in a pot to your right will be the Crest.
Transfiguration Courtyard
1. In the doorway to (I presume) Ravenclaw Tower.
2. On the wall to the right of the Transfiguration Classroom.
3. From the portrait, enter the courtyard to the right, turn around and check the wall to left of the archway
4. On a bench just outside the doorway leading to Herbology.
Transfiguration Classroom
1. Right above doorway.
Library
1. Head to the Restricted Section in the back. The Crest is visible in the fence.
2. On your way to the back of the Library, a Crest is between two bookshelves on the right.
3. Out in the corridor, right next to the desk. You need to repair this one.
4. From previous Crest, head down to the end of the hall. It's up on the wall.
5. From previous Crest, head to the stairway on your left. Crest is high up on the wall straight ahead as you walk in.
Viaduct Entrance
1. Above the huge double doors.
2. Above the entrance to the Potions Dungeon.
3. Behind the boar statue.
4. Head up the stairs and into the next corridor. Check behind some spiderwebs on your left.
5. Keep following the hall to the next door. Crest is above door.
Hospital Wing Corridor
1. On the wall to the left of the Hospital Wing.
Stone Bridge
1. Above one of the two doors.
2. On the ledge next to the door opposite the one with the crest.
3. Head through the door with the crest, follow the hall until given the option to go left. Check above the door down that hall.
Suspension Bridge
1. Above the door next to the Crest Statue
Grand Staircase
1. Proceed straight out of Gryffindor Tower and down the stairs to the left. Look at the wall at the bottom of the next set of steps.
2. When exiting the Library portrait, head up the stairs to your right.
3. Head all the way to the bottom of the stairs. Check underneath the stairs.
4. From previous crest, head up the nearby stairs, and instead of going right, keep going straight until you hit a dead end with the crest. - credit to MikeMan54
Floor 1 off Grand Staircase
1. Follow the curved hall, turning right after passing through an archway. Follow that hall to a door. Turn around after going through the door and check above the door
Floor 3 off Grand Staircase
1. Head down the stairs and into the curved hallway. Halfway through there will be a statue to your left holding a Crest.
2. Continue down the hall, and then down the stairs.Crest is in a gate beneath the stairs.
Floor 5 off Grand Staircase
1. Head down the stairs and through the door and turn around to check above the door.
Floor 7 off Grand Staircase
1. A Crest is in an alcove to the left of where the student drops the brass scales during your visit to find Malfoy.
2. Follow the hallway around until you see a Crest on the wall in front of you.
3. Double back and take the previous right. Go left down the next hall. Check the wall in the alcove to your right
4. Head back to where you got Crest one and proceed through the door. The statue standing above the stairs has a Crest.
5. From previous Crest, check the bottom of the stairs for a Crest sitting beside the fire.
6. From previous Crest, head into the cave. Halfway through there will be a Crest on the rocks to your right.
7. Further into the cave. Usually get on your trip with Luna.
Gryffindor Tower
1-2. On the walls in the common room.
3. Up in the boys dormitory.
Entrance Courtyard
1-2. One to the left and one to the right of the castle entrance.
3. Head out of the courtyard towards the Viaduct Entrance, but instead head into the alcove on the left and repair the broken Crest
4. From previous crest, head towards the Paved Courtyard. It will be on the wall on your left, covered by a plant.
5. Just outside and to the right of the Viaduct Entrance door.
6. Head to the stairs leading down to the Boathouse. When you reach the first turn in the stairs, turn around. Crest will be sitting on the ledge behind the window.
Paved Courtyard
1. When entering from the Grand Staircase, go into the curved corridor and turn around. Check above the door.
2. Keep following the corridor to reach the Paved Courtyard. Keep going straight and turn at the far corner. Crest is broken and straight ahead of you.
3. Head up the stairs in the courtyard and follow the path around to the next Crest. It's behind another plant on the wall.
4. In the tunnel leading to the Boathouse, on the wall to the left.
5. About halfway to the Boathouse from the Paved Courtyard there will be a Crest on the cliff to the left, covered by a plant
Boathouse
1. On the wall behind the Boathouse.
2. From previous Crest, above door at the base of the stairs to the left.
3. Halfway up the stairs leading back to the castle.
4. A little ways up the slope to the Paved Courtyard, there will be a crest hidden in a bush to the left
Hogwarts Grounds
1.Above the archway leading to the bridge.
2. When facing the bridge, look to the left. It's in a plant.
3. In a plant to the left of Hagrid's Hut.
4. On top of Hagrid's Hut.
5. Halfway across the bridge. You will get this while heading to the Quidditch tryouts.
6. On the left side of the path heading to the Owlery. Will get on your way to Quidditch tryouts.
7. Next to a tree a short ways behind Hagrid's Hut.
8. From Hagrid's Hut, head straight up the hill. The Crest is in a wooded alcove to the left.
Owlery
1. On the wall outside.
2. Behind the stairs when you first enter.
3. Head upstairs. Behind the stairs on the first platform.
4. Keep going upstairs. In the cage at the top
Quidditch Cave
1. On the wall straight ahead when entering beneath the Owlery.
2. On the ground just as you are coming to the underground pond place.
3. Head deeper into the cave. Eventually you will see it on the wall in front of you.
Clock Tower
1. Straight ahead, just behind the bells. Stand to the left and use Wingardium Leviosa.
2. From previous Crest, turn around. It's in a little alcove at the top of the steps.
Clock Tower Courtyard
1. Behind the ticker of the clock.
2. In pieces in the corner with the purple tree.
3. When facing the clock tower, in an alcove to the left.
4. When facing the bridge, on the wall to the left, covered by a plant.
Astronomy Tower
1. In the gate behind you when facing the corridor.
2. On the wall above the sliding bookcase.
3. Head out into the corridor and follow it around the far corner. Check above door.
4. From previous crest, head up the stairs. Head down the next set. Check behind the statur at the bottom.
5. From previous Crest, head into the hall and take a right. Follow the hall till you come to a door. Crest is in an alcove on your right.
Charms Classroom
1. On the wall to the right when entering.
2. In the seats to the left when entering.
Potions Dungeon
1. From the portrait, head to the room on the far right. Crest is inside the gate.
2. From previous Crest, head back out and take a left. Go left down the short steps then turn around. Crest is to the left of the center archway.
3. Head back through the archway then down to the left to the dead end. Crest (Slytherins Common Room is behind this wall)
4. To the right of the Slytherins Common Room is a spiderweb with a Crest behind it.
Firework Boxes:
Training Grounds on wall to the left of the Hufflepuff Dueling Board
Clock Tower Courtyard platfrom between the four statues
Hogwarts Grounds on your right just before entering the Quidditch Cave
Paved Courtyard up the steps on your way to Crest 3
See Paved Courtyard Crest 5 a little ways down, the box will be on your right
Banners:
Transfiguration Corridor start from entrance to Herbology
Transfiguration Courtyard from Transfiguration Corridor entrance, head all the way down the hall and turn right
See Viaduct Entrance Crest 4 turn around and hit the banners
See Floor 7 Crest 2 hit the banners as you proceed back down the hall
From Slughorn's Office on the 6th Floor head down the hall and turn right when given the chance. banners run down the hall on your next left
Statues:
Transfiguration Courtyard girl to the right of the portrait (when using portrait) - need to make a potion
Transfiguration Corridor guy by wall opposite statue - need to make potion
Library girl by the right bookcases in front of the portrait - need to make potion
Astronomy Tower Corridor girl close to door opposite statue - need to make a potion
Clock Tower Courtyard guy close to the portrait - need to make potion
Hagrid's Hut two students short way behind hut - duel
Training Grounds from Herbology entrance, run around the castle to the left and look for two students - duel
Clock Tower, Middle Floor head towards the Hospital Wing and look for two students - duel
Suspension Bridge look for two students - duel
Entrance Courtyard look for two students - duel