An overly long list of reminders for Tumblr:
Ignore replies similar to "I have something important to tell you but I can't dm you for some reason, I don't know why?" If you see one on somebody else's post, you can warn them that it's a scam. It will likely lead into the "I reported your account by accident!" DM.
Ignore anyone who tells you they reported your account by accident and needs your help to fix this. Don't press any of their links, don't put your sign in information anywhere they take you to, and don't speak with anyone they ask you to.
Be cautious of DMs from strangers that only say "hello," "hi," "how are you." Often, they won't be following you, or they followed you the moment they sent the message. You can still respond, just be aware that it may lead into a scam attempt.
It's generally advisable to state your reasoning for DMing someone from the start if you've never spoken before, as others will often ignore being just dm'd "hello" from a stranger.
Be cautious of links anyone sends you. A trusted person can still be hacked. People forget that even on Tumblr, certain links can still be used to get personal information out of you or scam you.
Be cautious of commission scams, especially if it's from somebody with a randomized username and no profile picture. I am less familiar with these, but I believe they go along the lines of someone showing no signs of knowing anything about you or your commission rules, but they want you to draw their pet and are insistent on overpaying you for it through their method of choice, wow, what a deal!
Have a profile picture! Especially if you do sincerely wish to comission someone! And don't be scared of looking like a scam for asking, so long as you have a blog that looks used, it should be fine. If someone has their commissions open, they want you to ask.
Do not share personal information that can be used against you, or that you could someday wish to take back sharing. Personal information may include the look of your car, the town you live in, photos of your town, your real name, your face. It's your choice to share, but information regarding your triggers and mental illnesses are safest in the hands of only people you trust.
Do not post your location plans, and do not confess to crimes (or your plans to commit a crime) on the internet.
You can hide or lie about personal details. It's okay. You can just do that. Anyone who pressures you into giving up those details is not a safe person.
Somebody who consistently makes you uncomfortable by pushing your boundaries is not displaying trust in you. They're displaying a lack of respect. In certain dynamics, these two concepts can grow muddled in your head.
If you are a minor on the internet, trust your gut if you do not feel 100% safe around someone. Don't be scared of how they'll feel or react. Regardless of age, you do not need to talk to anyone who makes you feel uncomfortable. Hit the bricks.
You can block whoever you want forever for anything.
You can mute someone without blocking them by typing their username into filtered content.
If you are a minor and somebody asks you to add them on or sign up for a messaging app/website, reassess this person's intentions as to why they cannot speak to you in public or where you met. If the app/website is a place where chat logs can be erased, do not do it under any circumstance. "I'd rather talk to you where there is no evidence" sounds a lot uglier when said plainly.
If you see a rainbow emoji next to a strawberry emoji, immediately block them. Remember this emoji combo.
If an anon sends a hate (or otherwise manipulative) ask regarding you or somebody else, there is no need for you to answer, even in defense. They are either attempting to use your blog to anonymously platform their statement, or are seeking a reaction.
No, you're not getting bad luck for not reblogging that post. No, you're not a bad person for not reblogging a post that demands it of you or tells you that you're a bad person for not reblogging it. It's fine. Take a breath. You have not come out of your Tumblr scroll a worse person, it's fine.
You can filter the "reblog bait" tag in an attempt to avoid posts that pressure you into reblogging them, though unfortunately not everyone will use this tag. You can also try filtering the content of certain common phrases from these posts.
If there's flashing lights in your video/gif, tag it with flashing lights. This is important. People can get hurt from these things being unwarned for. And do not tag it as epilepsy.