Find out which version of Ubuntu I am on

This article is rather old so the solutions may no longer work.

Recently (this morning) I had to find out which version of Ubuntu was running on a clients machine.  A quick google provided three articles of note all with different solutions.

1. Type cat /etc/issue into the command line (no back ticks).
2. Type lsb_release -a into the command line (no back ticks).
3. If you have a GUI, open up FireFox and view the about dialog.