I think by default people choose instances related to their region. That way you can communicate with likeminded people in the timeframe they’re the most active.
If not that then you look at the topics instance specialises in. For example:
- mander → science
- gtio → debate
- fapsi → creativity
- slrpnk → solar punk
- hackliberty → tech anarchism
- heapoverflow → programming etc
If you don’t care about specialization and prefer simply more content you choose general instance such as beehaw or sopuli
i would suggest looking mostly at who an instance federates with, how they handle data, and where they’re located (to know how much latency you’ll have, and also to see if the privacy laws there are sufficient). content doesn’t really matter unless you look at the local feed, because of federation
To be honest, I made accounts on a few and lurked for a while. I chose ones to make an account on based on size, aiming for the 200-500 active users range. If I decided I didn’t like a server’s vibe, I closed my account.
Also on Mastodon just choose an instance and if you find one that suits you better you can move your account there. Taking followers etc with you has been possible for 2 years now I think.
