There are a lot of studies that show that people, when they listen and respond to what the other person is saying rather than do the speaking about a topic, they tend to be looked at as great people to have conversations with.
In easier ways to look at it, there is a good conversation person, and a bad conversation person.
Studies have shown that if person A, listens to person B and just responds a little bit, enough to just have person B continue talking about topics and what interests them, person A is viewed as an awesome person to talk with by person B.
But, if person C likes to continue to lead the conversation and get most of the talk time, person B will look at person C as a boring person to have a conversation with, even though person C said more words.
In the first scenario in the study they did, person A said far less words than person C did in the second scenario, however, person A in the 1st scenario was regarded as a better listener, talker, etc. over person C.
Take this and flip it to the PUA world. If you get a girl to talk, ask her opinions, questions, and keep her talking about herself. Throw in comments here and there to make the conversation go. But she will look at you and be like, "omg I had an amazing conversation with this guy."
It doesn't mean let her lead the conversation to anything she wants, because you can easily lead it to the topic you want to talk about. It is just about guiding her motor boat (mouth) to what topic it is you want to discuss.