One of the first steps you should take when trying to establish more order among unruly collections, after ensuring security and mitigating catastrophic damage, is to to get a strong understanding of you have. It is essential to have a list of objects, or at least reasonable amounts of objects grouped together, in order to plan for their long-term storage!
Do you have an inventory, or checklist, or shelflist?
If not - plan to take one! Use the following spreadsheet for inspiration and feel free to modify it so that it works for you.
Keep in mind that the goal is to record what you have AND where you can find it. So you'll notice that locations are prominent in this spreadsheet. Label your shelves!
Contact me if you'd like to talk about how to use the inventory.
If you intend to take care of something, or some group of things, for the longer-term--let's say for at least 20 years--you will want to have a different collection management policy for them. Public Libraries have collection development policies for their general collections, but often they don't address their "special" collections. Consider crafting one.
Can you convene a group to develop some policies for your institution? I often suggest to convene collections committees to help make the process more collaborative, and to then to re-convene and re-assess the policies periodically. Should you or your committees want some guidance on how to approach long-term preservation of parts of the collections, please let me know!
In the end, you have to decide what you want to keep, and for how long. And that can be a difficult process. Collecting priorities certainly change over time, and with them, so should your collection development policies.
Mass Library System - MA Policy Collection - Local History Collection Development Policies: https://guides.masslibsystem.org/things/policies
Amherst College Library - Archives & Special Collections Collection Development Policy: https://www.amherst.edu/library/archives/collectiondevelopment.
You might consider drafting short additions to your policies to address any types of objects that are difficult to replace. They will have life cycles different from your circulating or Children's collections, so consider if they need special cataloging, shelving, boxing, labeling, lending, or maintenance policies. For example
See the Mass Library System's Policies & Resource Guide for Library of Things: https://guides.masslibsystem.org/things/policies.