Most of the writing groups I have participated in have been smaller, more intimate.
There was one that had about 10 members. We rotated from house to house with the host house providing light snacks, etc (just a perk) The host would choose a topic, or an excersise/prompt. We would write together then read aloud what we had written. We would then have general and specific conversation about writing, the projects we were working on, and what have you. This group worked well together so we stayed on topic. The main purpose of the group was to keep us writing, and motivated to do so.
We would also have nights where we would read from our works in progress, though this group was mostly writing practice.
Another one that I LOVED (and was cancelled
) had nights where we practiced in much the same way as I described. We always met in the same neutral location. The difference was that we would have 'focus' groups where one night was devoted to helping a member with a WIP, feedback, etc. This helped me SO much. This only worked bc it was a smal group (sometimes 2 or 3) Everyone had a turn being the focus.
The groups that didn't work were ones where we just talked about writing and did nothing else, they just petered out.
This is just from the top of my head. I have had ideas, but am not accessing them right now. I am thinking about starting up a group in my area.