Running the latest command as root (sudo)
In some cases when maintaining Linux/Unix systems, root privleges are needed for certain commands. And even though running applications as root can be a serious security threat, sometimes it is necessary.
You probably solved the typical "Permission denied" error at least once by simply repeating the command with "sudo" in front of it. If you need this often (perhaps you shouldn't), try this for a change:
The "!!" command basically repeats the previous command so you don't have to.
Xkcd also has a great article on sudo.
Sudo: Suck it Up and DO as i told.