To effectively troubleshoot and distinguish between failures in your own service and those caused by a Google Cloud service, you should consider both tracking cloud service errors and enabling Personalized Service Health annotations. Option A suggests creating a log-based metric to track cloud service errors, which is useful for identifying issues within Google Cloud services. Option D, enabling Personalized Service Health annotations, provides direct insights into Google Cloud service issues affecting your resources. While options B and C are useful for monitoring and alerting on system errors, they do not specifically help in distinguishing between your service's failures and those caused by Google Cloud services. Therefore, the most effective actions are A and D.