Get prepare with good concrete example of your ability of work
They may ask you about your previous accomplishments and you should be very well prepared for that.
I was not interviewed for uOttawa, I was brought on as a result of enthusiasm in the course I took previously. I was asked to come back by one of the teaching assistants from that year.
Within the CITE, my interview process was informal, and focused on assessing whether I could use my technical knowledge to minimize disruptions as quickly as possible for clients. You should be comfortable working with soundboards, and your attitude should be relaxed but solutions-oriented, since the clients themselves are likely to be stressed (at you/us) if something goes wrong.