About a decade ago I migrated into community work  from a non-community background. This is the guide I wish I had read back then.
 When I say community work, I am talking about stuff like Wikipedia: large distributed groups of people doing something together, usually online, often unpaid. Usually international, often nerdy, often (but not always) FLOSS or FLOSS-adjacent.
You are going to be doing a lot of writing. Do it well. Phone calls and Hangouts don’t scale. Face-to-face is expensive for distributed groups and therefore rare. Real-time tools like IRC and Slack disadvantage people in minority timezones. And so, in an online community, your main way to communicate is likely going to be email. Which means you need to be good at it. Take the time to write carefully, fully and precisely. And since text is going to do so much of your communicative heavy lifting, consider being a little more explicit about emotional signal-sending than you might be otherwise. (“I am happy…”, “it is sad…”, “I am grateful.”)
In all your communications, be conscious of your group’s diversity. The group you’re speaking with is likely more diverse than what you’re used to. There may be children and teenagers as well as adults. For many or most, English won’t be their first language. They probably live in multiple countries, have had a broad diversity of experiences, and and hold a wide array of beliefs. This creates a bunch of potential pitfalls. Your jokes may fall flat or offend people. Cultural references (sports, movies, history) may be meaningless. Even for those of us who aren’t American, it’s easy to come across as U.S.-centric. Metaphors, allusions and convoluted sentence structures may not be worth the time they’d take readers to untangle, and make translations much more difficult. High diversity argues for a style that’s literal, straightforward, and well-structured.
Be cautious about creating an insider culture. This is a tough one, because inside jokes and shared history and assumptions foster a sense of belonging. But every in-group requires an out-group, and having a lot of shared lore is unavoidably exclusionary: it makes it harder for new people to join. A strong culture will also inevitably move you towards demographic/attitudinal narrowing, rather than the reverse.
Publish early, publish often. If you are building a plan or a proposal, don’t wait until it’s flawless and polished to publish: release it while it’s still raw and half-baked. For folks from a non-community background this will feel dangerous, like you’re leaving yourself vulnerable to criticism. But in a community context it builds trust and empathy, and will be understood as an invitation to collaborate. Do tons of signposting. Explain what you’re trying to do, and why. Sketch out how you imagine it may work.
Be aware that volunteer time is different from paid time. Staff need to begin their public work as soon as they possibly can (sooner!), and to build in lots of elapsed time for community discussion. Community members have other priorities: school, jobs, families. You can’t expect them to make your work their top priority, so you need to give them the biggest-possible window in which to contribute.
Write (and publish) a greater volume of stuff than you think you should. This feels counter-intuitive for people who’ve been execs in traditional contexts, because in an ordinary executive context the scarcest resource is time, and so we get used to providing summaries, bullet points, upshots, and key takeaways. Succinct=good. In a community context though, comprehensive beats succinct. This is only logical: if you’re writing for a wide diversity of stakeholders, they’re going to want to know a wide variety of stuff. Manually asking and answering questions is slow and laborious and splinters the information so you can’t get it all in one place: it’s faster and better, as much as possible, to anticipate questions and answer them in your original communication.
Assume good faith. This is so easier said than done ;/ But for real, assume good faith. When someone asks a question and you think they are trolling, it’s entirely possible they are not. (Maybe they are 15 years old, or their English is imperfect, or they have an impairment of some kind.) Even if they are trolling: there will always be onlookers who don’t know it, and who, whatever the provocation, will recoil if you are curt or unkind. Trolling also gives you an opportunity to equip onlookers with reasonable arguments that they can go on to use themselves.
Bias towards transparency. Way, way, way more than you think you should. I remember being taught change management back in the early 2000s. Our instructor beat into us that wherever there is a communications vacuum, it will be filled by gossip and fear. That is a million percent true, and even more so in online communities. Gossip and fear grow out of power imbalances and information asymmetry which are to some degree unavoidable in distributed and voluntary groups, and you need to compensate for that. Publishing everything also scales well, because it equips everybody, not just you and your inner circle, to help explain what’s going on.
Note that if you’re the boss it’s insufficient to ask your staff to be transparent, because as long as there is any risk of penalty for over-publishing, they will do the opposite. You need to make it clear that nobody will ever be punished or shamed for being transparent, then you need somebody to publish something they shouldn’t have, and then you need to not punish them. Only then will people begin to take you seriously about transparency.
When you change your mind, say it publicly, and explain why. This is another one that’s tough for execs from a non-community context, where we got trained to express more confidence than we felt. But for real: in a community context, changing your mind and explaining why will not erode your credibility; it will earn you more.
Pay attention to people you disagree with. In an ordinary work environment executives get insulated and protected from honest disagreement. This is bad for them and for their company. Community work is different: there is no shortage of people who will disagree with you, loudly and repeatedly, in public. It’s natural to avoid or ignore those people, but if you do, you’re wasting an opportunity. Consider instead that they may, occasionally, be right.