Video Assist
On film sets in order to allow multiple people to watch what is being recorded on the cameras monitors will be set up for the director, producers , DP and script supervisor.
The person that operates, controls and manages this feed and makes sure it is set up and working is called a video assist.
To get to this position, you need to start out as a production assistant. On set make friends with the current video assist and find out how they got there.
You should learn all you can about technical side of filmmaking, for example; learn about all of the cameras, what monitors are used, how to set them up, and most importantly how to troubleshoot when a feed is lost.
