So which do I pick if I've never read any Harry Potter book nor seen any Harry Potter movie?
WINDED EXPLANATION NOBODY WANTED
Gryffindor: Brave, tend toward being good & noble, but often overconfident or naive (Ron Weasley is the quintessential one in the books)
Hufflepuff: Loyal, caring, make friends easily. Tend to let people walk all over them or not stand out. (As evidenced by how few factor in to the story)
Ravenclaw: Intelligent and/or creative, but often lacking social skills or being awkward (Luna Lovegood is the perfect representation of both sides)
Slytherin: Cunning, calculating, generally excellent in social situations. However, they tend toward being dark and manipulative. Most of the villains in the series are Slytherins. (Draco Malfoy represents the house well)
Of course, as we learn in the books, the Sorting Hat chooses houses partially based on the wearer's choice, so if you will yourself toward one you probably end up in it. (Choice being a key important element of the story)
