1.) Print Screen button - this will capture the entire desktop.
2.) Alt + Print Screen button - this will capture the current active window.
3.) You can also invoke the gnome-screenshot application via the Accessories menu which gives you a bit more control.
I tend to use the gnome-screenshot application the most and wanted a quick way of invoking it without traversing the menus. This howto shows how to assign the CTRL + Print Screen keyboard combination to the gnome-screenshot application (the example below was done with Ubuntu Netbook Edition).
Step 1: Open the Keyboard preferences via the Preference menu.
Step 2 Add shortcut.
Choose and name and then put the following in the command: gnome-screenshot --interactive
Step 3 Select Key Binding.
After the add you should see your entry under "Custom Shortcuts". Put the mouse cursor over the shortcut section of the line and click. You should now be able to pick any key combination you wish. I my case I choose CTRL + Print.
