If you can come up with a "Vision" or "Problem" statement you can begin to guess at some of the requirements you might need. Here is a URL to Moore's Vision statement: http://newsletter.beaupre.com/e_article000209887.cfm
After you get a vision/problem statement together, setup a small brainstorming session with interested parties to come up with some ideas about requirements. After the session and a break you sit down and boil those preliminary requirements into some kind of draft narrative that you derive your flow-chart/demo from.
If you have some competence in web pages you could produce a slightly interactive prototype.
Jan 18, 2010
How To Make Process Flow Diagrams by: Dee Reavis
In order to create process flow diagram you need to learn the basic flowchart symbols. You will find the basic ones at http://www1.gantep.edu.tr/~andrew/ep241/lectures/images/flowchart.gif.
If you own Microsoft Word, you can use its Word Art add on. It has these basic symbols available.
Once you have your flow diagram constructed, you can either save your Word document or create a jpeg image using print screen and Gimp or Photoshop.
With that basic document you can create a presentation in Microsoft Powerpoint.
That is the basic approach that I would use to create a process flow diagram and a demo.