Best practices
Make it easy to use your app with iCloud.
Avoid asking which documents to keep in iCloud.
Keep content up to date when possible.
Respect iCloud storage space.
Make sure your app behaves appropriately when iCloud is unavailable.
Keep app state information in iCloud.
Warn about the consequences of deleting a document.
Make conflict resolution prompt and easy.
Include iCloud content in search results.
For games, consider saving player progress in iCloud.
For the complete guidance, including worked examples and illustrations, see the canonical page: https://developer.apple.com/design/human-interface-guidelines/icloud