How Can We Encourage Debate?

Having a healthy, respectful, robust debate takes more than simply having an opinion and a loud voice. If I make a list of what is needed to have a good dialogue, what would that list contain?

In an era of polarized opinions on a number of topics including politics, religion, health care, gun control, immigration, abortion, and several other issues, how can we have a debate in which opposing sides actually listen to each other?

How can we encourage debate?

Related questions: How can we turn ideas into actions? What is necessary to change your mind? When is doubt helpful? How do you know who to trust?