Hurn-ia
As squibbler states, in the end it is the course manager and other higher powers that decide your fate. All I can say from personal experience is that I wanted ADC/APR and I made sure instructors etc knew this. Not too sure if it helped, but I was chosen for ADC.
Don't mean to sound negative
but I think you have very little control on what you end up doing. When you make your final decision, let others know, do your very best at the college and hope that the instructors etc all know how keen and dedicated you are to the job. It worked for me, but maybe that was just coincidence!
By the way, when do you find out who has been chosen for each discipline?
Away from home