To toggle a service from starting or stopping permanently you would need to:
echo manual | sudo tee /etc/init/SERVICE.override
where the stanza manual will stop Upstart from automatically loading the service on next boot. Any service with the .override ending will take precedence over the original service file. You will only be able to start the service manually afterwards. If you do not want this then simply delete the .override. For example:
echo manual | sudo tee /etc/init/mysql.override