Honourable mention

Mobile apps have become an international phenomenon and localization doesn’t just mean localizing text into whatever language is used in a particular geographic region.

If your app, or the back-end service that powers the app, needs to address the customer in any way, you need to diligently localize that too.

This is especially true for non-English speaking countries where it is reasonable to assume they have different naming conventions and styles of address, e.g. Japan or Germany.

You also need to ensure you don’t run afoul of courtesy titles or honourifics, e.g. “Mr” in a country where only credentialed professionals may use such a prefix.