For me it was just a matter of reading tutorials and learning the command line -- mostly everyday stuff for me anyway. I just learned how to tweak Ubuntu with installing certain programs and don't worry if you break your system -- that's how I learned Linux. You also want to learn how to do things with the command line and learn to REALLY use it, as in in case X crashes, you can navigate and fix the problem with the command line only. That way you can work your way around many problems.
So basically, just read tutorials and you'll learn. At least that's what I did.
EDIT: Oh and if you're thinking the command line in Linux is at all like DOS, stop thinking that. Bash (the command line in Linux) is twenty thousand more times powerful than DOS.
Edited by akiratheoni, 24 February 2008 - 10:08 PM.