Find out what graphics card you have and:
Applications > Add/Remove... > System tools + Supported applications, search 'driver' and check the box for NVidia or ATI binary X.org driver ('Hardware Drivers' (gnome) should already be checked I think)
System > Administration > Hardware drivers, there check the checkbox for graphics driver.
If ATI Radeon then you can also search for 'catalyst' (Other + All available) and install ATI Catalyst Control Center which will be under Applications > Other
At least that's how I did it.