I have looked at the official sites documentation, and it is a little tough to find starting points.
Is there a free comprehensive guide that is easy to understand for someone that has never dealt with mod_security?
Server Fault is a question and answer site for system and network administrators. It only takes a minute to sign up.Sign up to join this community
How about ModSecurity for Apache User Guide? It's a little dated, but I am sure it has plenty of relevant information.
It's not free, but the "ModSecurity 2.5" book is pretty good. Here's the Slashdot review: http://books.slashdot.org/story/10/01/13/1424213/ModSecurity-25?from=rss