The other day, I was chatting with a classmate on the subway and the topic of writing groups came up. As writers, people are always telling us "you need to get feedback on your work" but it's not always easy to find the right group. I myself have been working with my group, Quill & Coffee, for over two years and while I may not be an expert on all writer's groups, I can say things that have worked for us.
Rule #1: There are no rules. Our group is much more free-form than a class or workshop, governed solely by our mutual respect for each other as readers and writers. Of course, as things evolved over the years, we have added in some rules (we now have a page limit and a double-space rule) and have established something akin to a schedule. But we started with a clean slate and only one guideline: if something doesn't work for you... speak up. This style may not work for all groups, but it's worked for us.
Rule #2: Embrace your diversity as writers. Often, writers like to band together with other writers in their genre, writers who "get" what they're trying to say. I have found, though, that reading work in different genres and getting feedback from writers who may not be familiar with middle grade or teen fiction can be as valuable as getting critiques from fellow children's writers.
Rule #3: Take initiative. Our group works because different group members take initiative over different aspects of running the group. When we decided we needed to switch locations, one group member scouted out possible new places. Another writer always sends out "reminder" emails, letting the group know when the next meeting is, who's submitting, etc. My job in the group? I'm the resident supplier of writing exercises; I bring one to every meeting, in case we have time left over at the end.
As for finding the right group in the first place... that's the tricky part. Writing classes, conferences, or your local library are all good places to start. In the end, keep an open mind and give yourself a few meetings to get a sense of the group before you decide for sure if it's the right group for you. And, of course, if you can't find a group that suits your style, you can always start your own!