Hi Renarde,
Closed meetings are for alcoholics only, as opposed to open meetings, which anyone can attend. Most of the meetings in my area are open meetings, but I do attend some closed ones as well. They are basically the same format.
You do not have to go to a beginners meeting for your first meeting. But I would highly recommend you check one out, as they tend to focus on the first three steps, i.e., the steps that directly address not drinking. I have almost 8 months sober and I still usually go to one beginners meeting a week.
You do not need to prepare in any way.
You do not have to talk if you don't want to. Usually, in the beginning of a meeting, the chairperson will ask if it's anyone's first AA meeting ever, or if it's anyone's first time at that particular meeting. If you wish, you can just raise your hand and say your first name. That's it. But you don't have to if you don't want to.
What people talk about is dependent on what kind of meeting it is. If it's a big book meeting, people will read and discuss a chapter or portion of the book. If it's a speaker meeting, then someone will tell their story and people can comment after. If it's a discussion/topic meeting, then the chairperson will choose a topic, maybe share a little bit, and then turn it over for the group to share.
I've only been to one meeting where they actually go around the room and everyone introduces themselves. This was a beginners meeting. If you don't feel comfortable saying your name, you can always say pass.
My advice to you? Just go in with an open mind. And if you're up to it, raise your hand hand when they ask if anyone is new. Some meetings will pass around beginners packets so you can get people's numbers and some AA info. It's also a good idea to hang around after the meeting for a bit and just chat with some people. Trust me, everyone will be nice and welcome you accordingly. It's always good to start building some connections with people and get a few phone numbers to call. But again, this isn't a requirement. If you want to bolt right after, that's your prerogative. Do what makes you feel comfortable.
Let us know how it goes!