This tutorial has been written as a memo for the setup of upstart jobs under Linux distributions.
Indeed, some services (e.g. openssh-server, mysql-server, vsftpd), installed via the packages are automatically launched via upstart jobs. This tutorial shows how to disable these services from being automatically started.
Preventing services from auto-starting
To prevent these services from auto-starting, just add the keyword "never" to the list of "start on".
Here is an example for MySQL. The following is an extract of the initial /etc/init/mysql.conf script:
start on (net-device-up and local-filesystems and runlevel ) stop on runlevel 
To prevent MySQL from autostarting, just add:
start on (never and net-device-up and local-filesystems and runlevel ) stop on runlevel