I stopped scrolling for this?

Shit You Must Do Right Fucking Now:

Change your profile picture, blog header, and title to something other than the defaults. Do it right now. You will be mistaken for a bot otherwise, and blocked.

Go into Settings -> Dashboard, scroll down to Preferences, and turn off the options in the picture. This will get rid of most of the algorithmic stuff.

Turn off Tumblr Live. You have to snooze it once every 7 days for some stupid reason. It's hosted through another company and will steal your data if you use it.

Go to your blog settings (under the little person menu) and turn off these two settings:

Turn off infinite scroll (lags the site) and turn on timestamps on posts, in the same menu as Preferences.

Basic Features of the Site:

Reblogs drive the entire site. If you'd upvote something on Reddit, you'd reblog it on Tumblr. You can add text, images, or tags to a reblog, but you're not required to.

The dashboard is the equivalent to your Reddit feed, and contains the posts of all the people you follow, with the newest at the top

You can send an ask to someone, and it'll appear in their askbox for them to answer. You can receive them too, or turn off the settings if you don't want.

Tags aren't actually used for finding stuff (search function is dogshit), but are more for categorizing. People also talk in tags. Because Tumblr is weird, you can't use quotation marks (") or commas in them without fucking it up

You can filter both tags and phrases under Account Settings; doing this will put a filter over a post that contains them, which you'll have to click through to see the post itself. Useful for avoiding hate speech or blocking out annoying stuff

You can make polls in posts. Here's one now.

Likes are useless. They literally do fuck-all except send a notification to the OP.

Stuff Tumblr Does That Other Sites Don't:

Very old posts (I'm talking from like 2012) often circulate on this site. There's no such thing as a post being "too old" to reblog

Blocking is highly encouraged; you can block someone for any reason. Even for just being annoying.

If you and someone else are following each other, you are mutuals. Mutuals are fucking awesome and are treasured like friends. Mutuals are a thing on other sites but Tumblr treats em differently.

You can screenshot someone's tags if you like them and add them to a reblog. This is called "peer review"

Sometimes someone will find a blog and go through it and like/reblog a bunch of posts. This is totally fine and not "creepy" like it is seen as on other sites.

Tumblr jokes often rely on Continuing The Bit and a "yes, and?" attitude. Goncharov is probably the best example of this.

We are fucking infested with bots. They will either have totally blank profiles or be filled with porn. Block and report on sight.

Censorship is pretty lax here. I can say "I want to brutally stab Elon Musk to death and watch him bleed out in front of a crowd" and nobody gives a shit.

General Etiquette:

Don't try to do epic clapbacks here, you'll probably just get laughed at or blocked. If someone is bugging you or spouting bigoted bullshit, block them.

Reblog art!!! Artists often struggle to gain traction on here; reblogging will give them a boost.

Not every reblog needs a comment or tag in it

You can go all out with tagging your stuff to organize it, or you can just leave it all blank. Someone might ask "hey, can you tag these posts as [x]?" and you can decide if you want to do that or not. It's generally polite to oblige, but "no" is still reasonable.

Avoid discourse like the plague. Filter it, block people who start it, scroll past it when you see it. Just don't get involved in it. Ever.

Don't put fandom tags or jokes on someone's posts about serious matters or personal shit

You're responsible for curating your own dashboard; if you complain about constantly seeing stuff you don't like, that's probably on you. Don't be afraid to unfollow.

Follower count doesn't matter much here and you don't have to make yours known if you don't want to.

Reblog, don't repost. Reblogging keeps the credit and doesn't "steal" engagement like Twitter retweets.

If someone likes something a LOT, they might reblog it like 30 times in a row. This is normal

Having a post blow up is actually kinda a bad thing, since it floods your notifications. There's a sort of in-joke about how having a big post is awful and people jokingly try to stop their own posts from blowing up, often in vain.

Tips:

Get XKit Rewritten if you're on desktop, it's a really helpful extension

In the little drop-down menu next to the 'Post now' button you can either save a draft, schedule a post, or add it to your queue. The queue lets you post things in order at a certain interval, which you can change. It's good for spreading stuff out over time.

You can use Shift+R to quickly reblog stuff and Shift+Q to queue!

Filter your notifications under Activity - you can also see some neat graphs

Find each other! If you want your old Reddit communities to stick together, seek out other refugees and follow them.