Mastodon: Join us it's not hard.
Also Mastodon: Here's six links on how to pick a server, find friends, follow people, getting started & how you should act.
That being said,I heard a good analogy from @davatron5000 on Shop Talk Show podcast:
"#Mastodon is like a HOA (home owner's association) – you moved in and there's rules to the neighborhood… apply to get in… but result is a controlled atmosphere and less about seizing chaos which is a lot about what OTHER social networks are about."