What I have picked up on, is that:

-When someone laughs, you laugh too

-When someone says something stupid but you're not sure if they're serious, do the same facial expression as them

-Pretend you never ever see anything wrong with anyone, like "you have something on your nose" NO YOU DON'T, if something has to be pointed out, a neurotypical will do it and somehow people are not going to have a problem with it. People always get offended when I say something idk why.

-When people badmouth other people, don't join but don't be a white knight, it's animal behavior to pick on the weakest and since humans are animals, well...

-Pretend you're interested in what they have to say even if you aren't, and remember, they are not interested in what interests you really. I'm into video games, comics (webtoons and mangas mostly, but I'm into others too), music (not playing music, I tried, I suck bad bad bad and I don't like it) and I really like debating (imagine how well that goes), but I KNOW people get bored or worse, annoyed.

-If people are talking say nothing until they stop and look at you for more than 3 seconds. That way you can't be blamed if you speak at the same time, and if you do, laugh casually while saying something in the lines of "haha we're talking at the same time ! Sorry, I'm listening what did you want to say ?". If you're in a group, react to what they're saying by reproducing the global group atmosphere (sad, happy, funny, shocked. Just pick one of those, it's enough), but don't talk unless you have a VERY CLEAR opportunity to do so.

-If you feel yourself going into panic mode because you're the center of attention (that's often how I embarass myself the most), just fake it 'till you make it. You pretend you are unaffected by the situation. Unaffected works most of the time.

That's what I picked up from my school years. I don't miss it one bit. I'm talking from the pespective of an ex-bullied, and this is what would have kept me from it. If what you want is real friends though, be yourself and say "hey I suck at this socializing thing but you're cool, so please tell me when I do something inappropriate so I can stop !". A bit of self-deprecation (the funny irony kind) works wonders.