I was in your position once. Went to my first Reddit meetup. Thought it was going to be awkward (and it was for a while). There were all sorts of people there. There were neckbeards and people who only talked about memes and people who came to boast about how popular they are with women (and unsuccessfully hit on the couple of women who showed up) and even a guy who was really into furries. But importantly there were people like me, who were anxious but just wanted to have a chat and a drink and talk about video games and movies and university. Made a good friend there actually (that was only temporary, but that's besides the point).
I'm no pro, but I can try to give you some tips:
before you go try your best to PM the meetup organiser and get his number so you can text him when you're nearby and make it easier to find the group.
try to get there early. It's easier to mix in when there are only a couple of people there rather than when the group gets too big and everyone is already busy with their own conversations.
your opener is always going to be "hi my name is .... What's your's?". Shake their hand if you're cool with that.
before you go to the meetup, sit down with a pen and paper and think of some "canned material" i.e. questions you can ask to get the conversation rolling when you feel stuck. Examples: Is this your first Reddit meetup? How long have you been on Reddit? Have you lived in this city for long? What do you do at work? What do you do when not at work? Do you like <some shit I like>? Have you heard this joke?
ask the above questions. Accept that with some people, even an extroverted social butterfly would have a hard time making conversation. Some people are just like that, it's their fault not yours. Move on to the next person in the group and introduce yourself.
know in your mind that if it gets to be too much for you, you can get up and leave. Even if you've only been there 5 minutes and don't like what you see.
also try meetup.com, there you can find activity groups. It's easier if everyone is there for a hike or some such activity rather than just being at a bar face to face with a drink being forced to make constant conversation.
Good luck bro. You did better and took a bigger step than a lot of other shy people manage to. You're smart and insightful enough to know what you don't like about your situation and you're actively doing something to change that. I think that's awesome.