How I did it: I was looking to meet others in my metro area with a particular niche interest, but wasn't having any luck. I had run a meetup several years ago, and thought I would give it a try.
Around January of every year, Meetup.com does a 50% off coupon, so the cost of startup is fairly low if you go with a 6-month plan. (They also have a 30-day guarantee if you cancel your group within that time, but I believe that 30 days is not enough time to know whether a group is going to work.)
Setting up your group is absolutely critical. You get a limited number of interests to tag your group with, and about 3 days after you create your group, an announcement message will go out - only once! - to folks who have indicated an interest in any of those topics. So you need to have that list of topics determined either in advance, or immediately upon creation of the group. You want to attract people with general topics, but you also need to make sure you have the bases covered of your specific niche (if you have one). You also need a catchy but short-ish description, and not too many rules.
Which brings me to my successful meetup theory - I believe that meetups with a very specific description do better than vague ones, except for singles meetups. I have seen several failing meetups, and almost always they don't have a clear enough idea of what they want to be - an artists' meetup that just suggests "getting together and doing art," or a coffee meetup that is just about "drinking coffee." What's the hook? What makes it worth people's time to come to your group instead of the many other options?
You should schedule an event before the announcement goes out, so that when people join your group, they can keep up the momentum by RSVPing for the event. I scheduled events roughly every 3 weeks to start, and now I have roughly 1 event per week, although sub-groups have formed that tend to go to some events and not others, so it's not like the same people show to everything.
I post a Greeting on the page of every new member who joins, welcoming them and directing them to various resources we use.
I print an attendance list for every event, and try to memorize names and faces so I can greet new folks. I make a point of sitting/hanging out with new people so I can gauge their interest and answer any questions. If there are going to be a lot of new folks, I enlist my husband or another existing member to help me greet and make new folks comfortable.
I send an email to new folks after they attend their first event, thanking them for coming and following up on anything I said I'd get back to them on (I often am asked to provide links to resources we have discussed).
I also advertised the group on Craigslist, and on message boards related to the topic of my Meetup. I don't think much came from CL, but the message board thing was very helpful. I tried hard not to be spammy about it.
Openness to suggestions and not being a dictator is very important. I think that being clear that my role is faciitator, not ruler, makes people comfortable.
At the six month mark, when dues came due, I asked for donations, no obligation, and received far more than I asked for. I said I would use overage for a group event, and I accounted for all donations publicly (but anonymously). Transparency is critical - people get cranky if they think you're trying to turn a profit.
We are now well over 100 members, with several successful events every month, and I feel like we are doing really well. I have made lots of friends, including a couple really good ones, and I've exercised my social muscles as well. :) Read how I did it… 21 months ago