iptables install/config for a standalone single-IP system

[whatzdaname]

First off, I'm a total newbie in the net security business.

I have seen increasing unauthorized access to my Gentoo machine these days and I decided to install a firewall for my system. What I would ultimately like to do is to manually block all the IPs trying to break into my machine - or use any method equivalent to that effect.

I read over the "HOWTO: Iptables for newbies" parts 1 and 2 in the Docs, Tips, & Tricks section but didn't understand lots of things -- I realized it might be because the HOWTO is dealing with a situation not suited for my situation. I have a standalone single-IP system and I would like to set up iptables for my system to block specific IPs. Anyone giving me tips would be greatly appreciated.

PS I have tried using shorewall but I can't find a way to block specific IPs.

Thanks.

[SoTired]