How to make a linux server as a router

I have installed redhat linux 9.0. I want to make it as a router. I have a 128k leased line for internet. I want to connect one NIC to my Lan which has connection to the internet router and another NIC where my LAN and I want to do routing so that everybody should go through my Linux server and directly to the internet router. What should I do and how should I do