Appendix: In Which Miss Greengrass Explains Things to Miss Granger
Gryffindor House is a band of adventurers. Your Head of House is your captain. She handles large-scale strategy and sends you off on your quests, but otherwise she leaves you pretty much alone. Your housemates are your comrades in arms. You watch each other's backs in a fight, but you're heroes, not soldiers. You don't follow orders properly and you don't maintain military discipline, so you're vulnerable to well-organized opposition. Everyone admires you, but no one counts on you in a pinch.
Hufflepuff House is a family. Their Head of House is their mother, who loves and supports them all. Even when the Head is a man, he's the mother. The housemates are siblings; they'll always support one another no matter what, but they quarrel among themselves and compete for their mother's attention. Everyone relies on them but no one notices them except when they're being annoying.
Ravenclaw House is a research academy. The Head of House is the director; he guides the research and makes sure everyone follows proper methodology. The housemates are colleagues. They love to share information and ideas, but they want credit for their own work. They're always watching one another for plagiarism and wrangling over tiny details. Everyone respects them and recognizes their usefulness, but no one likes them much.
Slytherin House is a political party. Our Head of House is the leader of the party; he sets policy, but he can't really go against the over-all consensus of the House. Our housemates are our fellow party members. In the face of our opponents we keep party discipline. Our number one rule is, "Thou shalt not speak ill of a fellow Slytherin." The rule doesn't apply in-house, though. There, we're always working for our own advantage and trading favors. We don't have friends, we have allies; we don't have enemies, we have opponents; and the alliances are always shifting. Everyone is suspicious of us, but they come to us to do the dirty work that really has to be done and no one else will touch. We do it, no matter what it takes, and no one thanks us for it, or thinks to repay the favor when we're the ones who need help.
I wrote this some months ago to be a part of "Hermione Granger and the House of Slytherin", a story still in the planning stages. If that story is ever written, Miss Granger of Slytherin will be Explaining Things to Mr Potter of Gryffindor in the Hospital Wing after an incident in which a misplaced troll is dispatched by a couple of quick Sectumsempras from Hermione's Head of House. Don't expect it soon. I don't even have a full outline yet, and the spirit of Mr. Gilbert will not permit me to write on the fly. Everything must be completed and polished before the first chapter appears. My apologies, but one does not argue with Mr. Gilbert on such matters.