Co-operative societies are formed voluntarily by people who wish to jointly pursue economic goals which they could not achieve as individuals. Such societies are commonly formed by consumers, for example, and in fields such as agriculture and housing construction. The concepts of self-organisation, self-help and solidarity play a major role in co-operative societies. They can therefore be used as an instructive example of how to implement local democracy in practical terms for the benefit of all members of a group. The present paper gives an overview of this concept.