This is NOT a tutorial but a series of personal notes (jottings) to remember what to do to save time.
Examples vary from beginner to advanced (eg. how to rename files from a digital camera, how to find a regular expression and replace it in all files of recursive directories, etc).
To find out more about the use of a piece of software and its options check man pages or respective web-sites; they provide exhaustive tutorials and up-to-date information (which can be daunting if you need to find the right page on the net because you're just trying to remember the command that made it so easy to convert pictures to thumbnails... hence the initial need for this file).
While I started these jottings for my personal use I have since realised many friends were keen on GNU Linux and needed some sort of flash cards to get cracking. Hope this will be a start for your own jottings.