When you need to update data stored in localStorage, you should always follow a clear sequence: retrieve the value, parse it if it is in JSON format, make your changes, then stringify and save it back. This approach ensures you never accidentally corrupt the stored data or lose information. For arrays and objects, always use JSON.parse to convert the stored string back to a usable JavaScript value, make your updates, and then use JSON.stringify when saving. Avoid trying to directly modify values in storage, as localStorage only stores strings and does not provide methods for in-place editing. Always overwrite the existing key with the updated stringified value to maintain consistency and prevent data errors.