Hi and well done for deciding to go! It's nothing to be worried about. The first half hour of the meeting is usually for weighing. You are weighed by the leader (or a trained helper - but for your first 5 weeks it will be with the leader) and then you just sit down and wait. Not everyone will stay after being weighed. The for the second half hour the leader will talk to everyone. They will usually ask who is pleased this week and why, or who is disappointed and why. Just sharing experiences really. Then each week they have a topic that WW gives them which they talk about. I didn't get to my meeting today until 10 mins before the end and it looked like they were talking about what is really in the food and misleading claims about the health benefits etc - like was does 'light' or 'low fat' really mean.
Then after this everyone will leave and the leader will just explain the plan to any new members and answer any of their questions. So I'd say to expect to be there for over an hour for your first week.
My meetings are like the above, meeting would follow a schedule set by ww. The only thing I would add is that most of the 'talk' time is spent on the topic of the week only a short amount is talking to members and no one is put on the spot. If you have any issues you can raise then with the leader privately. I know a lot of people dont like the classes but I def benefit from them.