There are several best practices for monitoring and optimizing the performance of Elastic Load Balancers (ELB). Use Amazon CloudWatch to track ELB metrics such as request count, latency, and backend connection errors for insight into your application's performance and to set up alarms for anomaly detection. Enable access logs to analyze traffic patterns and identify potential security risks. To optimize performance, enable cross-zone load balancing to distribute traffic evenly across all registered instances and configure connection draining to maintain active sessions during instance de-registration. Use health checks to direct traffic away from unhealthy instances. Also, scale your backend resources appropriately to handle traffic spikes and utilize SSL offloading for better resource utilization.