I reccomend you go on monster.com and look up a security administrator.
Basically you should be good at the following:
DNS systems (bind, easyDNS, Windows Active directory, etc.)
User privleges (windows, linux, windows)
Web security means you have to understand web servers apache, IIS, etc...
Email security means you have to understand email systems Exchange, sendmail, postfix...
OS security and vulnrabilitys such as ports, memory leaks, etc.
File server privledges...
and finnaly database privledges...
So first understand how these servers work
then how to configure them properly
then how to justify those configurations
then how to hack systems
then how to make patches and work arounds.
Then you can adequately perform that job at the basic level.
Primary requirement to be a security guy: Trust. People have to trust you enough to let you know about security problems before they go public. Almost all security problems are reported -- to someone -- before they are exploited.