How to: Install Spotify in Ubuntu
http://haxordoubt.blogspot.com/2013/04/how-to-install-spotify-in-ubuntu.html
The following code will add the Spotify repository, authenticate it (which makes sure the software you install is the official one), checks for the latest version, and installs Spotify. You should copy and paste this code into your Terminal and execute it.
You can view these commands individually at the Official Spotify Linux Preview page.