To develop a virtual prototype, you will need to choose a prototyping technology that is cheap, easy, and will allow you to simply portray your concept to customers. You might consider using pencil and paper, a drawing program on your phone, tablet, or computer, Microsoft PowerPoint, Apple's Keynote, or any number of other similar technologies to create a virtual prototype. Below are some examples of virtual prototypes to help you get a feel for how it can be done.
a. Consumer Product: When testing out the concept for the Wii U controller, Nintendo first built a cardboard virtual prototype to see what the experience would be like. Later, they moved on to piecing together a rough actual prototype.
b. Software: In prototyping software, you can test out your hypotheses very easily without ever writing any code by just sketching up the basic idea on paper. After that, you can move on to using mockup software to wire frame and test an actual prototype - still without ever writing any code.
c. Website: Often, when you are looking to do a virtual prototype of a website, you can start with something as simple as diagrams and drawings that show what the website will do. An actual prototype can be simple as well. When the founder of Zappos.com was testing his idea, he never actually bought any inventory at all. Instead, he built a very basic website with pictures he took at a local shoe store. Then, when someone placed an order on the website, he would go to the shoe store, buy the shoes, and then ship them out. Doing it this way allowed him to quickly test his hypotheses that people would buy shoes online before investing a lot of time and money in inventory.
d. Mobile App: A quick virtual prototype for a mobile app can be as simple as getting a sheet of paper and drawing out some sample screen shots. Following that, a great way to make an actual prototype is to mock up the interaction and Minimum Feature Set in PowerPoint or Keynote. Oftentimes you can even export the file into a PDF that will include the links to view it on a mobile device, all without having to spend time or money on coding.
Remember, prototypes are NOT for you to see how your idea is coming along. It is for you to show customers in order to quickly and cheaply validate solutions to pain.
(See Nail It Then Scale It, pgs. 102-107)