In my experience (and I've had a lot with writers' groups), one of the hardest things about writers' critique groups is not so much finding writers, but getting together with ones that share your goals... or maybe a better term is: values.
Why is this important? Maybe it isn't for you. Maybe you're self-motivated enough that it won't matter to you that you might end up being the only one in your group who is interested in something beyond writing as a hobby (which there isn't anything wrong with, mind you. I fully support people who want to write just for the fun of it, and might only ever want to post the occasional bit of fanfic or political blog or just write privately in their own journals or whatever.) Perhaps you live in a town so small that getting two writers together -- even if one writes erotica and the other is a food journalist -- is the best you can hope for, so, well, then that's what you have and that can work for you. Support is support. As someone who was a member of the National Writers' Union before I broke in to fiction, I hung out with a lot of non-fiction writers and journalists. They taught me a lot about my craft, but even more about the value (economic and otherwise) of writing.
But, if you have the luxury and the inclination, it is nice to have a group that's all committed to the same sort of thing. I don't mean by this that everyone needs to be writing in the same genre (though that can help, particularly since both genres that I've published in get dissed and misunderstood by some,) or at the same level (I've learned a lot about writing by teaching others to write better.) But the biggest, most deeply fought fights I've had in writers' group have boiled down to two issues: Are we writing to be published? And, are we writing commercial or artistic work?
The two questions are kind of part of one whole, but you can be writing to be published and still consider your work art for art's sake with a goal of finding the perfect small press to put out your chapbook. There's room for all of that sort of stuff, but in my opinion, you get very different critiques from people who are "artists" and from those who want to sell.
My advice: decide what kind of writer you want to be, and try to find writers with similar goals (if possible, of course.) Maybe at your first meeting you can ask people that classic interview question about where they see themselves in ten years. The answers might be very illuminating about not only what they want, but who they are (and if you can get along with them professionally.)
Then you have to decide if you're tough enough to tell someone they're not right for your group... admittedly, I've found that difficult, myself. :-)