Hm, what makes a good server? I think for me, I want: not going to disappear, high uptime, low latency, moderate moderation.
You can measure moderation by going to most server's /about page, to see which servers they've limited interactions with.
I'm on hachyderm.io. It's good, but could be better. I expect it will remain at least at this baseline level of quality, so I'm too lazy to search out other options.
My wife is on wandering.shop. I'd say it struggles much more with latency/availability, but is still fine, especially if you use an app, which can paper over some of the latency issues.
I haven't tried it myself, but this purports to suggest a server based on some info about you (https://instances.social/). And (https://joinmastodon.org/servers) is kind of the "main" list.
I initially tried the https://joinmastodon.org/servers thing in November, but the things proposed seemed like very niche communities.
I just tried the https://instances.social/ link -- the top 2 hits for me were very small instances (fewer than 5 people), which I wouldn't have much faith in joining.
Actually, I guess I should have mentioned how I _actually_ chose a server. I used https://fedifinder.glitch.me/ and joined the first fast-enough server that most of my existing contacts were on.
So it's mostly like email. Logic that would work for email i think works for Mastodon. Just like with email you can generally email anyone and anyone emails you, the same applies to mastodon in my experience. However, if a server is being too <insert reason here> for your server's admins, they may block the entire thing. I don't know the finer details of how blocking can take place, but my loose belief is that you won't see posts from blocked servers. Though i may still be possible to explicitly follow someone on a blocked server.. i'm unclear there.
This amount of moderation will obviously vary from server to server. It is one of the criteria you'd look at for choosing a server.
Likewise local community is another, if you should care. There is a special Local feed, which i've found to be quite handy if the server you're on is specialized to a content type.
As for choosing your server, i think the above two points are useful metrics to help you decide. However if you're just looking to dip your toes in, pick any server. You can always decide to switch later, as you can set your old account to indicate that you moved to a different account. I've seen several accounts like this and it seems to be sane and easy.
So far i've been quite happy with Mastodon.
A small cool detail you didn't add: when you do that, anyone who was following you will automatically and seamlessly follow the new account.
Same for Truth Social.
ps. You can also follow hashtags if interested in a specific topic.
AFAIK, only if your server is on Mastodon 4.0.0 or newer, as Mastodon 3.x didn't have that feature yet.
Say you create the following named handle kd at server mas.to. If someone else would want to follow you, you'd just give that @kd@mas.to. Note that when you join a server, you'll have to abide by their rules.
It's easy enough to sync up follows.
Some small ones block the large ones (for their moderation policies), so having the small account will let you follow anyone, and the large can be a hedge if the smaller one becomes unstable