^SO well said! Agreed.
I'd also add- you don't have to speak, you don't have to identify yourself as a newcomer (a lot of mtgs ask if anyone is attending their first AA meeting, or is a visitor from another group) and you do not have to participate in the beginning or ending prayers most groups have (usually the Serenity Prayer and/or Lord's Prayer).
Also, you are not obligated to give the standard $1 to a basket that gets passed around. Visitors eat free, so to speak!
Lastly - you may want to look up the different kinds of meetings- personally, I would suggest trying different ones (places and types) and give yourself a chance to start understanding the program - typical codes by a mtg time are OD (Open Discussion- anyone is welcome, not just members of AA), CD (Closed Discussion, members only), 12/12 (Steps and Traditions), BB (Big Book), W (Womens) M (Mens) and the like.
Hope to hear how it goes! And- breathe. One step, one hour- that's all it is.