Ten Things Not To Do At Hogwarts
1) Do not offer anyone a cookie, if they have been in Dumbledore's office at all, they will get pissed at you
2) If you should forget and offer said cookie, don't offer them tea to try to make it better, they will be more pissed and may jinx you
3) Do not refuse said cookie or tea if you find your self in Dumbledore's office or he will be pissed.
4) You should not call the place between you legs your happiness
5) Or wand
6) Or snake, especially in the presence of a Slytherin
7) There is no spell to remove ones clothes or any one else's (Bet you wish you knew that before you paid two Galleons to get the spell )
8) Invisibly cloaks are not for sneaking in to the showers of the opposite sex
9) They are also not for watching members of the same sex in said showers
10) You should not tease Snape, he will kill you (or make you wish you were dead)