That is when there is often quick back and forth of "yes" and "no" type questions.
It is when you start to become genuinely interested in what the other person has to say that the conversation takes a life of its own.
It is best to choose a topic that you know a little bit about, so that you can follow the other person's response with your own point of view.
If the person responds to the open-ended question by saying that he has one sister, some potential follow-up questions might include the following: Once you are in the habit of asking follow-up questions, simply rinse and repeat.
Perhaps the most famous (or infamous) open-ended question is "How does this make you feel? This has become a cliché in both journalism and therapy.