Extracted from a comment on a previous post:
Does Miss Snark have any thoughts on critique groups? As in the thoughtful post of 10.2 regarding agents, is a bad one or the wrong one more harm than good?
Critique groups can be great. A couple of really really good writers I know came out of a long running writing group called "Dangerous Writers" that evolved from a class taught by Tom Spanbauer -among them Chuck Palahniuk (Fight Club), and Joanna Rose (Little Miss Strange).
I think it helps to have someone reading your work, and having to produce pages on a deadline. I also think if the wrong people are chomping on your work it can be deadly.
Writing groups can also be useless if it doesn't help you improve your work. Early in my career when I sent trying-to-be-of-help rejection letters I'd mention critique groups to writers who lacked really basic stuff..spelling, grammar, diction. One writer was so offended she wrote back and said she'd been in one for years. I almost laughed cause of course she'd missed the obvious conclusion; the group was wildly ineffectual if she was sending out work that made me think she needed one.
Sadly, I don't have clue one on how to find a good one and how to identify signs of a bad one.