Nagios configuration can either be your friend or your enemy. We recommend getting be friends with it as it can be a lifesaver.

When deploying Nagios in your company, it would be worthwhile planning the layout of your entire configuration. Some people recommend one file for each single definition, while others recommend storing things in a single file per host. We recommend keeping similar things in the same file and maintaining a directory-based set of files.

Defining parent hosts and dependencies between hosts and services would also be beneficial if you want Nagios to help you track down the root cause of a problem. This will skip check against hosts and services that are in error due to the other problems in your network. Of course, if you don't define those, Nagios will still work, will still perform very useful checks, but you will be on your own in analyzing what happened because of what.

In order for Nagios and you to get along well, it would also be good to use templates...