Well, I'd say they monitor the ratings of any given show. If the stats say the show is getting less and less viewers, then the show is in danger of cancellation. In tv, I am not sure how to help, but in places like Netflix, it helps if you keep watching what you love, as your show, if watched by many people, will beging trending and the executives will notice that people are loving it. I don't think many show producers care that much about the public. They care about making money, and if a show is not getting enough viewers to justify the expenses of the show, chances are they will cancel it, no matter how much a small fanbase rages and claims for more episodes.
