How to change network setting in Linux

I'm having a problem to access to my desktop using GUI. So, I decided to use command in console. I would like to share with people especially newbies how to configure Linux network using a command prompt based on my experience.

1. [root@localhost ~]#ifconfig eth0 172.20.30.30 netmask 255.255.255.0 up
2. [root@localhost ~]#route add default gw 172.20.30.254