What is the OOC space?
The OOC namespace is intended for you to store notes and other information which doesn't really suit an in-universe article, but which is important for you to have down somewhere nonetheless. What this is not for is OOC discussions. Both the main article Talk page and the OOC Talk page are for discussions. This is for information storage.
Are there any special rules?
Ideally you will still categorize and add interwiki links as normal, but as stated previously, OOC articles do not have a requirement for neutral point of view, objectivity, or to only provide knowable and in-universe information. There is no requirement for how you might format these articles, nor is there any reason to try to avoid having stub articles; though hopefully you will provide more than just stubs if you are making use of these pages.