A/N: Thank you etherian from Archive of Our Own for the Slytherin House Rules.
After Dumbledore gave his usual first-day of school speech and they were all fed and watered, the Prefects jumped up from their tables to lead their charges to the dormitory.
"Excuse me, I'm a prefect!" Marcus Flint bellowed. "First years, follow me!"
They followed him and a female prefect down to the dungeons.
The password is "Basilisk." The door opened and they clambered into the common room.
"Gather round, First years," Marcus said.
"Before our Head of House speaks to you, we are going to go over the House Rules. Damaria, do you want to start?" Marcus asked.
"Outside of our common room, Slytherin House is seen as evil and you will be bullied. Hence the first rule. Your House is your family and your family stays together. We have to present a united front outside of our common room," Damaria said.
"The common room doesn't belong to you," Marcus continued. "It belongs to everyone so keep it neat."
"Arguments with another Slytherin are only permitted in Slytherin House. Refer to the first rule on how to behave in public," Damaria lectured.
"Study time is quiet and mandatory. All Slytherins should be passing their classes," Marcus continued.
"No one is allowed to miss House Meetings which are almost always scheduled," She added.
"The Hogwarts House Elfs are not your servants," Marcus scolded. "Keeping your dorm rooms and the common room clean is your responsibility."
"Dorm inspections once a month. These are NOT scheduled," She warned, "You are forewarned."
"All meals are mandatory," he added. "No sweets in your dorms and no sweets past 8 pm."
Professor Snape walked in and said, "Those taking a Nutrition Potion will come to me or Madame Pomfrey once a week."
"Now about bedtimes: first years-9 p.m., second thru fourth years-10 p.m., fifth and sixth years-11 p.m. and seventh years-midnight," he lectured. "These are the rules I expect everyone in Slytherin House to follow to the letter. They are not however the only rules. During your seven years here, I will give you further rules and guidelines you can take with you beyond the walls of Hogwarts."
"Everyone recite with me the Secret of Slytherin," he finished.
"Plan in ways a Ravenclaw finds sound.
Blend in like a Hufflepuff in the background.
As for Gryffindor, learn from their mistakes.
And be ready, Slytherins, swift as a snake.
Serpens tacitus perspicasis et celeris est."
"Now to bed all of you," Snape added. "Good night."