Most town meeting are open to the public, BUT speaking at one usually requires you to be a resident, or at least a business owner. Typically you are put on a list to speak with a mark for which side you are on, they will use that to go back and forth. You start by stating you full name and the street you live on. Then you give you opinions/comments, this is NOT an argument, no back and forth. You address the committee or board, or the chair. You refer to past speakers as the past speaker, not by name. They will encourage you not to just repeat what someone else said, although you can just "I rise in support of" Start yelling from the crowd and they will be thrown out, or they will even close the meeting, don't be that guy. They will also ask you to hold any cheers or clapping, how strictly is up to the chair.
If you have never been to one of these and plan on going, do some searching, many towns have a video archive of past meetings you can watch to see how these work. Framingham has these, I'm sure others do, I just know about theirs's.