How do I change Ubuntu screen resolution?

All I'm getting is a horrible 800X600 resolution, and will not let me increase it any more. I'm a complete newbie to Ubuntu (first day of installation) so please bear this in mind with any instructions. Please help me! ThanksHow do I change Ubuntu screen resolution?
Have you installed the driver for your Graphics Card



NVIDIA CARDS



How to install Nvidia drivers on Ubuntu (installer on Ubuntu 8.10 upwards is slightly different. Install the recommended driver)

http://www.psychocats.net/ubuntu/nvidia



ATI CARDS



RadeonDriver

https://help.ubuntu.com/community/Radeon



RadeonXpress

https://help.ubuntu.com/community/Radeon





LUg.How do I change Ubuntu screen resolution?
first check for hardware drivers-System%26gt;Administration%26gt;hardware drivers .then check System%26gt; preferences%26gt; Display