You'll want to set up reporting. This will also tell you when a node has
stopped reporting or is otherwise struggling. Have a read through
http://docs.puppetlabs.com/guides/reporting.html . You'll also probably
want a pretty web frontend like Puppet Dashboard
(http://www.puppetlabs.com/puppet/related-projects/dashboard/) or The
Foreman (http://theforeman.org/)
Dan