No godmodding. If your char can perform Legilimancy, get permission from the other muns involved before reading any minds. If your chars are duelling, make sure you have permission for your spells to hit, or figure out how they get deflected. No physically throwing each other around without permission either.
Basically, permission, permission, permission! Get it. You'll like it. Consent is good, okay?
And to go along with that, no powerplaying. This is focused more on characters and character development than whose char is the most powerful.
Literacy is a requirement. There's no minimum post length but one-liners are strongly discouraged. The more you give in a post, the more the other person has to work off for their reply. Use third person, past tense, not asterisks, when RPing, and first person for journal entries.
Journal entries have different levels. Unless it's specified otherwise in the subject line, it's assumed the entry is open to everyone in that group. There are two groups. DEs cannot read the entries of Dumbledore's Army or vice versa unless the subject line says ::open to DEs:: or ::open to DA:: which'll indicate it was deliberately meant to be read by the other side. Apart from that, the entries can be screened for specific groups of people simply by putting ::open for only Luna, Neville and Ginny:: in the subject line or whatever the names are of the characters involved.
It's a game. IC is not OOC. Don't start huge flame wars, don't cry yourself to sleep, and remember, behind the character is a person. Just because a character hates yours doesn't mean the player hates you.
ICness is love.
Different timezones are not the fault of any of the players. Don't hold them responsible for not being on as often as you'd like or on during the wrong hours.
If you're going on hiatus for any length of time over a week, leave a comment in the ooc comm, sans_ooc.