A children's co-op is not limited to housewives; it can work for any group. Working couples or single-parent families could arrange child co-ops for weekends or nights only. Some pointers to get you started:

* Start small. Begin by forming a co-op with a friend or two. It is best to include, at first, those people whom you really know. Obtain new members through recommendations. "I have another friend who is interested in this idea," is the way most co-ops grow.

* Stay small. 15-20 members are adequate. This allows members to get to know each other and prevents cliques from forming.

* Formulate rules that meet the group's particular needs. Remember the rules serve only as a guideline and should benefit the majority.

* Change the rules when necessary. If something doesn't work, discuss it and find a better solution.

* Meet regularly. Monthly meetings allow members to stay in contact and build cohesiveness.

* Have up-to-date, notarized emergency release forms available for each child. These forms, which allow emergency treatment to be obtained for your child without your presence, are obtainable through your hospital.

* Send snacks, lunch, extra clothing, or whatever you think your child will need in your absence. If your child has a fear of dogs or an allergy to peanut butter, inform the sitter.

* Always include the phone number where you can be reached.

* Never send sick children or take in children when you or yours are sick. You might lose all your new-found friends.

* Be prompt in delivering and picking up children. The sitter has set aside a specific time period just for you.