The other day someone at a networking event said to me "Of course, the thing with networking is that it's all about finding the right group."
That's pretty much the exact opposite of what I believe.
Many people flit from group to group, looking for a magic format that's going to make everything work brilliantly for them right away. But it doesn't work like that. Really, all these groups are more or less rooms with people and coffee in them. If the people are idiots, then there's no format that's going to solve that. If the people are good, then they'll be able to work round any format, get to know one another, and make useful connections.
Over the years, we've been to various groups, and we've stuck with any where we've thought that there's a critical mass of good people, or where we just enjoy ourselves when we're there, without any particular expectation of financial benefit to our business. We've got something good out of all of those groups, whether in terms of enjoyment, useful connections for us and our clients (finding good people that we can recommend to our clients and to others is actually a more important aspect of networking to us than getting business for ourselves), and ultimately growing our business. With all of those successful groups, it's happened because we stuck with it and just talked and got to know people without expecting that this group was just going to do everything for us with its supposedly brilliant and ground-breaking format.
So, our recommendation: if you find a group that has a decent number of people going and not too many of them are idiots, then stick with it. It might get you business, it might get you friends, it might get you some interesting anecdotes, it might give you some support if you work alone, it might give you people to bounce ideas off, it might make you better at explaining concisely just what you do and the benefits you bring (it will definitely do that, in fact), but it will certainly do something for your business and for you as a person. If you keep going into new groups, getting to know people on a superficial level and then leaving again, little of that is likely to happen. Turning up consistently to something good is likely to be far better for you than searching endlessly for something perfect.