Welcome twitter users fleeing the absolute cesspool that twitter is going to become as Musk gets his way with his awful ideas! Things are better here, and hey, if you're an old user coming back, they've actually improved shit!
Here's a list of important notes for tumblr usage:
Don't censor words, particularly trigger warnings. Tumblr has a very functional blacklist (found in your settings) that can filter by post content and/or tags. But the word needs to actually be present for the filter to work. Censoring words like r*pe is actively harmful to people attempting to avoid those topics.
Use tags liberally, you have as many as you want, but don't tag unrelated shit. You'll get reported for spam really fast if you do.
Set an avatar and reblog things, otherwise you look like a bot.
You are not obligated to have your real name anywhere in your blog/bio/etc. Most people here use handles.
You can turn your ask box & anons on or off if you are experiencing any kind of harassment. You can also turn off replies on your posts, and turn off reblogs if you need to.
Tumblr has keyboard shortcuts on desktop. You can find them listed under the blog/account menu. Go learn them, they make life so much easier.
Reblog things. Seriously. Also set your dash in chronological order. You can maintain several blogs if need be, but reblogging things is normal, expected, and how you pass along stuff you enjoy.
The majority of people aren't reading your card/dni/blog bio before they reblog stuff. Posts get passed around and the OP often isn't the focal point of the post. Learn to live with it.
Fic writers: you have unlimited words, do not post fics as images.
Reblogs with comments/tags are encouraged. It's not like twitter's QRTs. The OP will see everything there. Know that before you comment.
You have a queue. This means you can set posts up ahead of time to run while you're busy. You can also completely ignore this and just spam your follows whenever you're online. Both are very commonplace
It's not weird to go through someone's blog and reblog old posts. That's actually very normal. If you add /chrono to the end of a tumblr page then you can view all the posts in chronological order to make this easier.
"Spam" liking and reblogging isn't a thing that is a problem. This is invented by people I do not understand. If someone claims this is a problem, they can learn how to turn off or manage their notifications.
The only form of promotional posts that tumblr has is "blaze". There is no ad targeting or any kind of invasions of privacy with blaze. You just get subjected to w/e someone wants to show you. If you want to give tumblr some money to help the company keep going and providing an alternative to twitter, it's not a bad way to do it. You can make people look at cat photos.
Also, we have fun colors here. Plus actual formatting ability. Use it!
People lie on here for fun. Don't accept everything you see at face value, check the reblogs/replies or google something if you're skeptical! Critical thinking is good!
Above all else, be chill, use your block button if you need to, and have fun.