Vanessa Van Edwards says don't just walk up to a group conversation. Wait for them to laugh or have an "aha" moment, then lightly touch someone's arm and ask, "You look like you're having a great time. May I join?" Timing your entry to their peak openness makes them more likely to let you in.
Never walk up to a group and just stand there. It doesn't work. And people often are like, what is this person doing here? So what you want to do is wait for a group to be in a moment of laughter or a moment of aha. Then you walk up, you touch someone lightly on the arm, and you say, you look like you're having a great time. May I join? There's something magical happening in that group. They're laughing at something. They're having an aha moment. That is their peak openness moment. And if you walk in and you ask for social help, you are going to tug on a part of their heartstring that's like, oh, of course you can join. Come. You know, we were just talking about how her dog just did this thing in her couch. It was so funny. Let me tell you.