Writers' groups can be small or large, structured or informal, specialized or general, but they all provide a forum for you to receive feedback for your work. Some writers' groups invite speakers or discuss other aspects of writing but for the most part, the chief function is to enable the members to tender their work to other sets of eyes. The major difference between writers' groups and workshops is that workshops are generally sponsored by an organization or educational institution while writers' groups operate much like any club of like-minded individuals. Some writers' groups are open to every genre, while others may be specialized; some have only a handful of members, while others do not limit the number attending; some charge dues and meet in public forums, while others are free and meet in homes; some groups are completely open while others require a vote to admit new members; meetings may be held weekly or monthly or anywhere in between.
Family and friends rarely make for good readers to provide impartial criticism for your work. Workshops and writers' groups afford a forum to obtain objective opinions. Despite certain benefits from having others comment on your work, many writers prefer not to share their work and it is never read by anyone else until the submission process begins.
The most important factor to consider in deciding upon a particular group is the one thing you probably won't be able to answer until after you join; that is, whether you feel comfortable with the other members. Unless you will be forming a new group consisting of people you already know or you are already acquainted with several of the members of an existing group, it's going to be a matter of showing up, giving it a try, and seeing how it works out. If you are uncomfortable, you should move on to another group.
Keep in mind that you have two sets of responsibilities as a member of a writers' group. For one thing, most groups require that you submit material to be read and critiqued. The second role you must play is that of a reader providing constructive criticism and commentary. Flattering the writer with accolades is not fulfilling your responsibility; you need to offer suggestions and it should go without saying that you must do this in a civil way.
Finding a Writers' Group
Because writing is a solitary endeavor, many writers have little or no contact with other writers. The editors, publishers, and agents writers come into contact with do not form a pool of potential members for a writers' group. However, you can often locate a writers' group in one of the following ways:
Workshops and classes
Search the Internet, especially links to writers' conferences
The section of the newspaper that lists community activities, groups, and meetings
Postings at libraries and bookstores
Other writers you know