It doesn’t take much, honestly, and is again more about not doing negative things as opposed to doing positive things, if it helps to see it that way.
If you’re putting out a very inward energy then that can make people avoid talking to you, even if they would like to but think you’re trying to be left alone. Like, if you’re nervous at a partner dancing thing you can go sit at a table far from the floor or you can stand beside the floor and watch. When you’re done dancing with someone, try to fire off a “I’m pretty new, do you know anyone who would be good dance with here?”. It doesn’t matter if you’re good at whatever it is you’re doing, people are drawn to those who have fun doing it.
You will have to do some stuff, of course. But it could be as small as smiling at a joke you overheard and maybe getting a “see, this guy gets it!” My roommate struggles to make friends at the Irish music jams we go to because they rarely engage with others and they’ll leave early without saying bye and stuff. They’re all super friendly, it doesn’t take much!
Another thing is that being a regular is helpful; people love recognizing other people. I remember the second time I went to a swing dance event and was jumped by someone saying “HA! We got you!”.
Ultimately you’ll learn this with practice. And remember that you don’t need to be everyone’s friend, not at all, just open to the possibility of making a new aquaintance.
Oh, and try to avoid one word answers. “Is this seat free?” “Absolutely, have a seat!”(and then you don’t need to do anything else if you don’t want to, but if they do then you’ve establish a positive energy.
