"#3: Poor root password choice
Okay, repeat after me: “The root password is the key to the
kingdom.” So why would you make the key to the kingdom simple
to crack? Sure, make your standard user password something you can
easily remember and/or type. But that root password — you
know, the one that’s protecting your enterprise database
server — give that a much higher difficulty level. Make that
password one you might have to store, encrypted, on a USB key,
requiring you to slide that USB key into the machine, mount it,
decrypt the password, and use it.
"#4: Avoiding the command line
No one wants to have to memorize a bunch of commands. And for the
most part, the GUI takes care of a vast majority of them. But there
are times when the command line is easier, faster, more secure, and
more reliable. Avoiding the command line should be considered a
cardinal sin of Linux administration. You should at least have a
solid understanding of how the command line works and a small
arsenal of commands you can use without having to RTFM. With a
small selection of command-line tools on top of the GUI tools, you
should be ready for just about anything."