It is only proper to state the obvious. You should never trust anyone's advice about configuration or security without running it past your own gray matter first. They might apply to you as written and they might need to be modified. Also, in any book of recipes or guide to successful living you know that there are simplified answers to complex questions and you should treat them as such. There is no substitute for real understanding.
Computer security is about protecting the data and availability of an association of hosts.
The key words are authentication, privacy, integrity, and trust. To understand computer security we have to understand the interrelationships among all of the hosts and services on our networks as well as the ways in which those hosts can be accessed. Tools that allow this kind of management are complex and usually expensive. A simple free software program that is in widespread use whose functionality is at least equal to commercial packages is cfengine. It runs on nearly every UNIX-like system and on NT with the cygwin tools installed.