An honest #newhere #feditips guide for all the current arrivals on Mastodon would read something like:

Welcome to the Fediverse, where we need no Space Karen to tear ourselves up!

If you're not sure what you're doing -- pick a big server like .social. Don't pick a server that is too restrictive if you want people from other servers to be able to follow you (i.e., don't pick .art).

If you're willing to try stuff out -- use multiple accounts.

If you're feeling adventurous -- try Calckey! We have it all: full search, quote posts, channels ... and all the
crazy stuff.

Don't use the official app, no matter what they tell you, especially if you want to customize your experience. Use 3rd party apps like Fedilab for Android. Use Elk for Desktop if you miss Twitter.