There’s a lot of factors to consider, enough factors that there’s no consensus on how you make this choice and at the end of the day you have to pick one and run with it.
A random list of some factors you could potentially consider before yolo’ing:
Is the admin team good? Are they power-tripping jerks? Are they ideologues who are likely to defederate the world for no sensible reason? Do they have a good head for policy? There’s no easy way to evaluate this, you have to look at the sidebar to see who the admins are, stalk their posts a bit, read the modlog for banned users (but he aware that moderation decisions are federated and anonymous so it can be hard to tell what mod did what), and you yourself have to be good enough at these things to recognize quality (or at least alignment with your own values).
Is the instance well-funded and is the admin team prepared to deal with the serious stuff like child-porn reports and subpoenas? Again, this is hard to check for. Basically, if an instance has been pretty big for years (there are only like 2 or 3 Lemmy instances like this and they’re all overloaded) or has the admin team run some other big service before?
Are the instance rules compatible with your topic? Don’t run a porn sub in an instance that bans porn. There are vibe concerns as well, like an edgelord meme community is not going to do well on a hyper-moderated safe-space-oriented instance.
Is the community topic geographically based? You might want to pick an instance homed in that geography. This can be eval’ed by using ip-lookup tools of the instance doesn’t advertise its geography.
Is the instance homed in a jurisdiction that has favorable laws for your topic? It’s better to host a community for sex-work or bourbon on an instance in a jurisdiction where those things are legal, rather than in the UAE.
Is there a topic instance that specializes in your topic? There’s a pathfinder TTRPG instance and a star trek instance, is there one for your topic? Note that topic-based instances can fail some other and more important criteria like being an experienced admin team. It’s possible that a topic instance is NOT the right choice, but it’s worth considering.
Is the server overloaded already? Mebbe pick a different one.
Is there already a well run community on another instance? Help that one grow, don’t splinter the community further.
There are many more factors to consider, and no one considers them all. Eventually you have to pick an instance that’s “good enough” and run with it. But those are some of the major factors one could consider if you’re willing to put in the non-trivial amount of effort required to evaluate them.
Ashtear