Be nice. We're all part of the same community, so be friendly, be welcoming, and generally be a nice person. Be someone that other people want to be around.
Be respectful and constructive. We're a very diverse group (95 countries and counting!), so we're not going to agree all the time. Remember to be respectful and constructive with your communication to your fellow GDG'ers. Don't get into flamewars, don't make personal attacks, don't vent or rant unconstructively. Everyone should take responsibility for the community and take the initiative to diffuse tension and stop a potential flamewar or negative thread as early as possible.
Be collaborative. Work together! We can learn a lot from each other. Share knowledge, update the wiki, help each other out.
Participate. This is YOUR community, so be a part of it! Join in on discussions, show up for in-person meetings regularly, offer feedback, and offer to help implement that feedback!
Step down considerately. If you're an organizer, or have some form of responsibility in running a GDG chapter (ie. you're running the website), be aware of your own constraints. We all know that life can get busy, so if you know that a new job or family situation will impact your ability to organize your group, find a way to step down gracefully. Make sure someone can take over for you, and transfer the relevant information (contacts, passwords, etc.) for a smooth transition.
Mailing Lists and Web Forums
In particular, please observe some basic etiquette for online discussions.
Think before you send. Does this message need to go to hundreds of people around the world?
Do not send messages to the whole list that only need to go to one person.
Keep off topic conversations to a minimum.
Do not send spam. Do not advertise or promote personal projects which are off topic.
When reading forums in digest form, please observe these rules when replying to preserve conversation threading in everyone's inbox.
Change the subject of your reply to match the actual subject of the message you are replying to.
Only include from the digest the pertinent part of the message you are responding to in your reply. There is no need to send the entire digest back to everyone on the list (including those of us that already received each message individually).
Alternatively, visit the web interface, find the post, and reply there.
Do not send automated "out of office" or "vacation" messages.