Having the Macintosh background I do, I found these quite hilarious and true!

1) they close an application's windows thinking the program has quit.
2) they'll download Firefox and then run the browser from the disk image and then not be able to throw away the disk image because the program is still running. See number 1.
3) .exe files lie scattered around the desktop from aborted downloads of Flash Player or some screensaver-cursor-spyware doodad.
4) untitled folder. untitled folder 2. untitled folder 3. untitled folder 4...
5) Using Safari's Google search field to get to hotmail.com.
6) Desktop Picture or Wallpaper is not a synonym for Screensaver.

Link: Common Mistakes Made by New Mac Users