The Main Rules of Slytherin House as found posted in the common room etched into a silver plaque stuck to the wall with a permanent Sticking Charm:
1. Your House is your family. Family stands together.
2. The common room does not belong to YOU. It belongs to everyone. Keep it neat.
3. Arguments with another Slytherin are only permitted in Slytherin House. Refer to the FIRST RULE.
4. Study time is QUIET time and is mandatory. You will receive schedules on a weekly basis.
5. NO ONE is allowed to skip House meetings. House Meetings are almost always scheduled.
7. The Hogwarts House Elfs are not your servants. Keeping your dorm rooms and the common room clean is your responsibility.
8. Dorm inspections once a month. These are NOT scheduled. You are forewarned.
9. All meals are mandatory. No sweets in your dorms. No sweets after 8pm. Those taking a Nutrition Potion will come to me or Madame Pomfrey once a week.
10. Bedtimes: First years - 9pm
Second thru Fourth years - 10pm
Fifth thru Sixth years - 11pm
Seventh years - Midnight
11. Your House is your family. Family stands together.
These are the rules I expect everyone in Slytherin to follow; to the letter. They are, however, not the only rules. You will discover in your seven years here that I will give you further guidelines and rules that you can take past the walls of Hogwarts.
Finally, never forget the Secret of Slytherin:
Plan in ways a Ravenclaw finds sound
Blend like a Hufflepuff into the background
As for the Gryffindor, learn from their mistakes
And be ready to react, Slytherin, swift as a snake.
Serpens tacitus perspicasis et celeris est
Professor S. Snape