server monitoring

I've got Nagios and Munin up and running for my infrastructure. Now I've got to figure out how to best utilize those tools so that I'm not wasting system resources in the process of monitoring the system!

I searched on "nagios" and "munin" to see if there were any posts that already addressed this question. I didn't find any that answered my specific questions. But, for the sake of starting out by adding some value with this post, here is the list of things that are at least relevant:
http://www.guidelightsolutions.com/blog/enhancing-nagios-monitor-drupal-...