Idea Trees are a tool to help think about and organize ideas and discussions. Use them for brainstorming, outlining, project planning, debates and more. This Idea Tree teaches how to make Idea Trees:
Click the image to expand, or view the PDF which allows copy/pasting text.
More Tree Info
Discussion Trees with Example has info in the discussion below the post, too.
Tree creation software suggestions: MindNode (Mac, iOS), XMind (Windows, Mac, iOS, Android, Linux), or iThoughts (Windows, Mac, iOS). (If you can't pay, get XMind.)