Policies have several functions in today’s complex organizations. Their statement help define the values of the organization, and they help managers and staff translate those values into service priorities. Policies establish a standard for services that can be understood by users of the service and providers. Policies ensure equitable treatment for all, and polices provide a framework for delivery of services. When policies have been adopted by a library’s governing agents in a formal process and are consistent with local, state, and federal laws, they will be enforceable.
So, you should probably start with contacting the library development office of your state library. The staff in that office will help you with policies that build on the laws in your state. Next, review the Positions and Public Policy Statements approved by the Council of the American Library Association. These cover such topics as Services and Responsibilities of Libraries, Intellectual Freedom, Library Personnel Practices, and Library Services for the Poor. When you reference these, be sure to cite the most current version. In some cases, it might be also helpful to review the background documents for an individual policy; when these exist, they are part of the Policy Reference Manual, linked from the main policy page.
A web search using the terms "sample library policies" will quickly provide many examples.