Use the Keyboard Shortcuts tool in GNOME to customize the default keyboard shortcuts for your system. If you have a laptop that has special media buttons you can configure them here as well. In some distributions such as Ubuntu these media buttons may be automatically configured but you may still need to fine tune them to suit your needs.
To access this menu in from the GNOME desktop open the following menu:
System -> Preferences -> System Shortcuts
There are 3 groups of shortcuts you can customize: Sound, Desktop, and Window Management. These groups break down in the following way.
Sound – Deals with media players and system sound.
Desktop – Shortcuts for opening applications and managing menus.
Window Management – Shortcuts for working with windows and workspaces.
To make a change select the shortcut from the menu and enter the new combination, it should correctly appear as you have pressed it. If you are configuring media buttons press them here instead. To disable a shortcut select the shortcut from the menu and press backspace.