Monitoring Jenkins effectively involves addressing several key aspects such as RAM usage, CPU consumption, garbage collection, pipeline build failures, and security issues. RAM issues can arise from increased data size, memory leaks, and improper heap size configurations, while CPU spikes may be caused by inefficient processing or infinite loops, both of which require careful monitoring and adjustment of JVM parameters. Garbage collection, an essential memory management tool, can be optimized through tuning and the use of the G1GC collector to avoid excessive pause times. For pipeline build failures, a master and agent architecture is recommended to distribute workloads, and reliance on third-party plugins should be managed carefully to ensure stability and security. Lastly, securing Jenkins involves enforcing user authentication, access control policies, and utilizing security plugins to safeguard valuable credentials, all while maintaining comprehensive logging for system and build activities to ensure the health and efficiency of Jenkins operations.