What goes in the Collection? Acquisition and Weeding.

What goes into any library collection depends on the type of library.

School Libraries will focus on texts, resources, and materials intended to assist their age-group of students learn. This School Collection Policy from the Urban School of San Francisco is one sample for what a simple policy can look like. There are no specifics for titles or duration in it. Those are left to the Library staff.
School Library Collection Development is a site put together by a retired school librarian and gives access to 54 separate sites covering such topics as: Collection Development- Web Sites, School Library Collection Policies, Collection Evaluation and Weeding, and Preservation and Repair. The sites range from text and articles to videos that teach important skills.

When it comes to Academic Libraries, most Universities and Colleges post their policies online. A few that may be of interest are: Columbia University Collection Policy, University Of Prince Edward Island, Robertson Library Collection Policy, University of British Columbia Collection Policy. There are many others.

Special Libraries come in so many formats that while the broadest outlines of the policies listed above may apply to some of them, it is certain that they do not apply to all. No matter where you are you can rely on some people being more willing to acquire than to weed, and others to weed than acquire.

Sorry, but that's human nature.