Information required please

Hello,

I've recently supped up my firewall from the basic script that i got from a very good, popular HOW TO. I've come to understand that thing can be brought even firther to protect from many different attacks.

Where can I get information on such things and the rules neccessary. And other rulesets that woudl not come in a basic script, yet any server (esp. a web server) should have.

Thank you
Arturo P.