Do they write/store them within the app bundle/package itself? Or some other canonical location? Or does there not seem to be any standard?
Files usually go in
~/Library/Application Support/Your App/. Preferences go in
NEVER modify a file inside your own app bundle.
You should decidedly not write files into your app bundle at runtime. There's no guarantee that a user running your app will have permission to modify it. As Chris said, support files go in Application Support and preferences go in ~/Library/Preferences. To find the user's Application Support folder, you can use the
NSSearchPathForDirectoriesInDomains() function. To write preference files, you can use the NSUserDefaults or CFPreferences APIs.