Get the card by feeding the Puffskein
Get 800 points de-gnoming the burrow
Find the card in the forest near the burrow
Get the remembrall
Find the card in the Hogwarts Express tunnels
Defeat the Whomping Willow
Defeat the Whomping Willow without taking damage
Find the card in the only secret area inside Hogwarts which isn't in bookshelves
Find the card in a secret area in eastern hall
Find the card in a secret area in the library
Trade 50 beans for the card
Win the herbology race cup
Win the herbology lesson cup
Find the card in a secret area in the upper castle
Find the card in a secret area in knights' room
Find the card in a secret area in the gallery
Win the defense against dark arts race cup
Win the defense against dark arts lesson cup
Collect the card in the common room after getting all the cups
Defeat Peeves
Defeat Peeves without taking damage
Get 800 points de-gnoming the pumpkin patch
Survive Myrtle's item throwing without taking damage
Get an A in Verdimillious Duo
Find the card in a secret area in the dark forest
Collect all the beans in all areas of the dungeons, including the Slytherin chase
Collect all the beans in the Burrow and the Floo Powder slide
Collect all the beans in all areas of the castle grounds, including the dark forest (see comments)
Defeat Aragog
Defeat Aragog without taking damage
Find the card in a secret area near Gryffindor's common room
Find the card in a secret area near Lockhart's office
Win the duel against Hufflepuff
Win the duel against Ravenclaw
Win the duel against Slytherin
Enter the room where the sketchbook is
Get the Flipendo Duo
Collect all the beans in all areas of the upper castle
Collect all the beans in all areas of Hogwarts' ground floor (see comments)
Collect all the chocolate frogs and drink all the Wiggenweld potions
Defeat the basilisk
Defeat the basilisk without taking damage
Win the Quidditch cup