Write the moderation rules before you need them
Every moderation decision made in the middle of an argument looks like favouritism, because it is. You made it while annoyed.
Write down, in advance:
— What gets removed, specifically. Not "be respectful" — the actual categories, in plain language.
— What gets a warning and what gets an immediate removal.
— Whether removals are announced or silent. Pick one and stay consistent. Inconsistency is what people notice.
— Who has authority to remove, and who reviews it.
— How somebody appeals, and to whom.
— What you do with criticism aimed at you, which is the clause everyone conveniently forgets to write.
Then publish it somewhere findable. Not because people will read it — they will not — but because when you enforce it you can point at a rule that existed before the argument did.
The rules do not have to be liberal or strict. They have to be predictable.
Consistent and slightly wrong beats fair and unpredictable.

The first hour decides what the thread becomes
Comment sections set their tone early and then defend it. Whatever the first handful of comments are, the rest tend to match.
So the first hour is not optional:
— Be present. Reply to the first comments, briefly and specifically. Not a like. Words.
— Answer the first question properly, even if it is basic. Everyone reading is learning whether questions get answered here.
— If the first comment is hostile, respond calmly and factually once. That single reply sets the ceiling for how hostile the rest gets.
— If the first comment is excellent, say why it is good. Publicly rewarded behaviour repeats.
— Do not argue in the first hour. Whatever you do in that window becomes the theme of the thread.
If you cannot be around for an hour after publishing, publish later. A post you cannot tend to is a post you are handing to whoever shows up first.
Show up early or inherit whatever forms without you.