I like fwbuilder. Its a GUI front end to a number of different firewalls, including iptables. It basically allows you to define your rulesets graphically and then compile them into a script which will run the appropriate iptables commands. You can then see exactly what commands are used to create the firewall you configure.
The interface is sort of reminiscent (at least to me) of the Firewall-1 configuration tool. You will need to be somewhat used to configuring firewalls to use it properly...
Its probably a good way to start before trying to configure iptables at the command line (which should be the end goal, so you can modify firewall settings of a host you have compromised from the command line)



