I belong to two guilds. One a friend and I started. We put up a notice at the local fabric store and several people showed up. We keep it very informal and have had lots of people join up. We now have 32 members.
the second is larger around 75, its harder to get close to people in a large group. I tried to volunteer to help with quilt show etc, took a bit but people warmed up after a few months.
6 of us get together about once a month and sometimes more. we also go to shows etc as a group.