I've created a smaller version of my original doc, "Roll Your Own Firewall", so as to get right to the point. However, the concept of a short doc when talking about firewalls is a bit of an oxymoron.
SUPERMIKE'S KICKING FIREWALL TUTORIAL
I. ROCKET FAST FIREWALL PRIMER
Let's get to the point. You have a new Linux or Unix PC, and you want a firewall on it without something that confuses you nor sprays files all over your hard drive in unknown places. You don't want to use something third-party, and you want to improve it meticulously as you learn how to do so. SuperMike is going to hook you up!