How do TV producers/directors/screenwriters find out how their fans feel about their show?

[Natalie Sandoval]

I'm asking because I'd like have to my opinion about a show voiced and heard. As an example of what I mean, if the producer/writer (not sure who's in charge of these things) were to introduce a new character, and this character is majorly disliked by the fan-base, then the producer would have that character killed or otherwise taken off the show, right? The writers try to appease their fans. But how is it that they found out about the fans' opinions? Do they stalk the show's forums, or is there somewhere specifically that fans can go to voice their thoughts and where the writers are sure to notice? Or is this done the old fashion way, by sending in letters?

I'd appreciate any answer. Thank you in advance.