There can be many types of women's circles, for networking, for business and for play. Here at the Sisters of the Circle , we come together for personal growth and spiritual development. There are no rules except what you together decide. 
I like the following from www.millionthcircle.org

CIRCLE GUIDELINES
To participate in a circle, all you need is the desire, the willingness to attend the gatherings and to agree to follow circle principles. Each group determines their own guidelines. Following are some agreements that have helped circles
to function more successfully for all participants.

Create a circle.

Consider it a sacred space.

One person speaks at a time.

Speak and listen from the heart.

Encourage and welcome diverse points of view.

Listen with discernment instead of judgment.

Share leadership and resources.

Decide together how decisions will be made.

Work toward consensus when possible.

Offer experience instead of advice.  (Make "I" statements, not "you" statements.)

When in doubt or need, pause and silently ask for guidance.

Decide together what is to be held in confidence.

Speak from your own experience and beliefs rather than speaking for others.  (Make "I" statements, not "she" or "they" statements.)

Open and close the circle by hearing each voice. (Check-ins and check-outs.)

CIRCLE PRINCIPLES
The following are some suggested guidelines for a circle:

Create sacred space. This includes physically preparing a space to accommodate the participants in a circle, usually with a centerpiece or altar.

Listen with compassion and for wisdom. This includes listening without an agenda, suspending judgment, being curious and finding the underlying meaning in others' statements. Also, it is listening for wisdom as it comes through each participant.

Speak from your heart and experience. Speak one at a time. This includes saying what is true for you and speaking to the center of the circle, not to another individual. We offer our experience and feelings to the circle, not our advice. Also, we speak one at a time and invoke a talking piece, such as a talking stick, when needed, to ensure that all are heard.

Invite silence and reflection when needed, in you and in the circle. This includes listening to our own inner guidance before speaking. Also, we request silence and reflection in the circle when we feel it is needed.

Take responsibility for your experience and your impact on the circle. This includes demonstrating self-respect and self-restraint. We self-monitor to ensure that our needs and expectations are being met. We ensure our contribution adds to the positive experience of all in the circle.

Keep the confidence of the circle. This refers to our confidentiality agreements. What is spoken in the circle, stays in the circle to help ensure a safe environment for sharing our experiences and feelings.

Make decisions, when needed, by consensus. This refers to our decision making process. Should a circle need to make a decision, it is generally desirable tocome to a consensus. These guidelines can be used as a starting point for group agreements in any circle, knowing that each group will add or delete as they see fit.

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It is because I was initially impacted by Dr. Jean Shinoda Bolen's book, The Millionth Circle , that I refer to her material here. It is a good book to read together at circle as well.

Other sister circles include the more indigenous, using as structure The Thirteen Original Clan Mothers: Your Sacred Path to Discovering the Gifts, Talents, and Abilities of the Feminine by Jamie Sams .