Main one is applicable to any online space.

Hang back when you check out a new place. Get a feel for things before jumping in because, like reddit, not only does lemmy have a culture, each instance does, and each community on each instance does.

You go to a meme community in one place and crack a dark joke, everyone laughs. You do it on another, you get banned. Yet another and you're in a flame war.

But it doesn't just apply to things that controversial. It can be simple things like calling someone dude. Or talking about cars, or dogs, or weather. Sometimes, in some places, there's a culture that isn't obvious until you've scrolled through for a while. Again, this isn't specific to lemmy, or even only online.

Always do a vibe check when you're new somewhere, anywhere.