You can find quite a lot of files in /etc/sysconfig however in configuring them you may have trouble but there is a file that you can use to understand what attributes you can use for each file. It is sysconfig.txt. In my current Redhat 5.4 system the file is at the following location as it comes with the package initscripts.

For example if you want to set ethernet options into your ifcfg-eth0 file below is the quote from this file;