This is just a short list of useful and not so useful bits of knowledge I've managed to collect this week:
1. Configuring GRUB
Some Linux distros come with a GUI that lets you configure GRUB (the menu at the start that lets you choose which system to boot.) Mepis doesn't include that GUI. However, it is easy to configure GRUB manually with Kedit (as root). Just go to /boot/grub/menu.lst and cut and paste the system you want to boot as default right below the line "gfxmenu /boot/grub/message" (see the illustration).
You can also edit the language of the menu by editing the lines beginning with the word "title." To edit the boot menu timeout, simply change the value after the word "timeout."
2. Virtual command shells
In the case you want to go from a graphical session to a text session, simply press CTRL + ALT + F1. That will open a virtual command shell that will let you pass commands...and it may be a great boss key, too! :P To return to a graphical session, press CTRL + ALT + F7 (your windows and programs will be unaltered!) Also, in the case of frozen windows (I've never experienced such case on Mepis), you may press CTRL + ALT + Backspace instead of rebooting. I've heard it helps sometimes.
3. Fun with Konsole
Open your terminal and enter the following commands:
$ cal -3 : It will display a pretty nice and handy calendar
$ uname -a : It will display some useful info about your system (the kernel, the OS, the processor) and also the date and time
$ date --date='xx yyy' +%A (xx represents a number and yyy represents a month) : It will tell you which day your birthday will be this year! Mine will be on a Thursday! :P