Or for an even more reliable way, call your intro script driectly from the
player's init field.
This is
always the first thing executed when a mission starts.
Also, bear in mind that if you want to start your intro script from the init.sqs, for anything created in the
intro section of the editor, the script will need to be called: 'initintro.sqs'.
init.sqs will automatically run at the beginning of the mission.
initintro.sqs will automatically run at the beginning of the intro
Hope that helps you out.