Here in Liverpool we've been running a local group called SWIG for nearly a year now. Every month on the last Thursday, like yours.

What we learned quickly was that a regular schedule and location is important. Then it's all about promotion and making it interesting enough for all attendees. So we pitch our chat and talks at different levels and have Q&A sessions where more experienced experts can help out.

Numbers wise we typically get 14 to 24 attendees.

And now this month we have our first bigSWIG - http://interconnectit.com/3161/bigswig/ which is a paid for event, a little like a WordCamp in that we have speakers, but without the WordCamp overhead. We have space for 120 people (at a squeeze) but will be happy if 60 or so attend. From the sales so far I expect is to easily make this. But it's a heck of a change from free to paid for - you have to work harder on getting the right speakers, the venue, and the facilities.

We'll be streaming the event life as well, so you guys on t'other side of t'Atlantic can watch for free :-)