Just stumbled across a cool site, it offers quite detailed instructions for port setup for a bunch of routers (all kind of brands and all sorts of applications, games etc).
Now you can just refer your friends here instead of having to write them detailed instructions 🙂 neat..
Give it a spin at; http://portforward.com/
an example for a netgear router can be found here;
http://portforward.com/english/routers/port_forwarding/Netgear/CG814W/CG814Windex.htm