A lot of young people have extreme difficulty socializing. If you are on the spectrum, meeting people can be like looking for a ham sandwich on a Kosher vegan menu.
I'm going to blame our digital paradise for many of our social ills. In the old days, when your friends weren't words and pictures on a screen, kids learned how to act and interact around other people. Parents took kids to a local carnival, stood in line to buy tickets, watched all the fun stuff going on, then stood in line to get on a ride. Sometimes you were seated with people you don't know. That is exposure to society.
In the old days, people would actually knock on your door or ring the doorbell. When you opened the door, you would hear why the person came to your house. They were looking for donations, delivering a package requiring a signature, looking for your brother or sister, asking you to buy cookies, dropping something off for your mother, or promoting a religion. Each example of exposure was an exercise in simple communication with another person be they a stranger or an acquaintance. I somehow managed to survive each encounter unharmed. In our paranoid America, we shun strangers who approach us and we rarely interact. There goes your early childhood learning about polite behavior and language, how to listen and respond, and what the outside world is doing today.
Socializing on any level requires participation. You learn from doing. Socializing isn't a pass/fail test. In the old days, most kids learned these skills before the age of 10. We learned to write messages down on a piece of paper. We learned how to say "thank you" when there was a transaction. We followed what was being said to us and we followed up with questions if they were deemed important or pertinent. We would ask clerks in stores for help. We would talk to people in the check-out line about the cover of an absurd magazine. We talked to strangers waiting for the same bus. We would send away for a free gift from a breakfast cereal company with a coupon and a written letter. These are some of the ways we learned to interact with other people.
If you interact in person, you are learning a lot about other people in general. It's much easier to talk to people when you have a physical environment around you that is the same for both. You learn about the different kinds of personalities that people may possess, and you learn that some people can be sad, or happy, for reasons that are unrelated to you. Sometimes you would run into a neighborhood friend who introduces you to their cousin who goes to a different school. Each new encounter was a lesson in communication and socializing.
The only way to socialize is to be around other people. For some reason, some young adults believe that there is a map or a route to a specific place where they will make a friend. I have to say that there is no map, but the ideas shared here on the forum are the ones people believe might lead to an opportunity to socialize. That is the best start. You have to be around people. There is no special phrase that will guarantee a positive response from a stranger. There is no rehearsal and no magic phrases to help you socialize. Your own spontaneous nature should suffice. Being your natural self is the best approach.
People socialize differently in any of 100 different settings. Without the childhood experiences of interacting with lots of different people, you have no choice but to start doing so in your adult years. Kids learn from mistakes more easily than adults. They are more resilient and have an easier time reflecting on what they did wrong or what they forgot to do. As an adult, you have a richer vocabulary and you have some experience in some small-talk or responses to comments. Kids tend to blurt out whatever they are thinking. Kids are excused for that more often than adults. I know that I can make unusual comments or ask peculiar questions from time to time. I'm just curious about things. That causes different reactions from people. That is normal. Some people don't like having strangers talk to them. In my experience, though, most people have no problem interacting with a stranger, as long as you don't come across like a stalker.
But don’t like the classroom atmosphere as I was bullied in middle school & dealt with rowdy kids. Also don’t like the pressure of competing for women. And don’t know how to find those classes anyway.
Your middle school days are over and the bullies are somewhere else now. In a night school class, you won't be competing with anyone to pick up girls. You are there to meet people and perhaps learn what is being taught. In the process, you have a chance to socialize with other people and perhaps make a new friend. Start with that. Through this process, you will better understand how to effectively socialize with others. The point behind joining a group event is that it gives you the opportunity to see people, talk to them, and share a few stories about yourself and what the class means to you. The atmosphere is likely to be relaxed. You might consider taking a class in cooking or some kind of art. There is a lot of activity and people always interact with comments about what they are trying to do and pose questions to you about what you are doing. An interactive activity class would be best for you in my opinion. The worst that can happen is that you learn how to make the perfect Spanish omelet.
Social anxiety can be terrorizing, but if you seek to socialize, you must be among people. It takes some people a lot of time to warm up to strangers. An activity in a relaxed atmosphere is the best for everyone. You are not going to be the only nervous person in the room. People on this forum have a lot of ideas to help people minimize anxiety and sample quality social situations. Choose the ones that seem to suit you best. You have to participate to make things happen.