If you know someone who wants to sign up on Mastodon and the Fediverse, you might want to suggest this guide:
It's been reformatted to make it as easy as possible to sign up on a good reliable server.
If someone finds choice overwhelming, it suggests a good general server (which changes regularly).
If someone appreciates choice, there is a server directory with over 100 good servers organised into categories.
There is also a FAQ about signing up.