At the beginning, I want to introduce myself to the talking partner and than lead him to the theme of the conversation. I found it is easier to ask a question to lead him. Then I imagined what he will probably answer. After that I offer three random choices of response. And there I found that if I want to keep him on line I should ask a question each time after I respond him, so he can go along the route I designed, otherwise the talk becomes ridiculous.
The regular expressions are wonderful in themselves. But it is not easy at all to create a reasonable talk. E.g. here I want to go on a talk on travel. It seems that I have to go on asking questions to confine the topic, i.e. I have to lead the talk all the time, otherwise it will be nonsense. Even in this way, it doesn't go anywhere. I should ask one question in each response. It's not natural at all. On the contrary, it is like a one way of questions and answers. Of course, I think it has something to do the limit of my knowledge of them.