What's the best approach / process to advise users of when discussing how to keep their document libraries and sites within their site quotas? (OnPrem instance)
it is little very much open ended question. When user asked us about the quota increase, here what i do
- If versionning enabled then limit it( i forced them for max 4 version)
- delete the unused data(documents, sites etc)
- Empty the recycle-bin.
if they are using SharePoint as storage place you may force them to different tools(if you company has)
Ask them why they need more storage.