Microsoft Flight Simulator is a low cost way to introduce what it is like to fly without having to go to an airport.   In particular, it is a good way to show what would happen during a Young Eagle Flight.   Because of this, to demonstrate Microsoft Flight Simulator I typically select the local airport for the airport and a Cessna 172 for the type of airplane.   While doing this it is a good time to explain the parts of an airplane, the function of these parts and the instrument panel.
To make the session using Microsoft Flight Simulator more enjoyable, the following three things are encouraged.
A good companion to demonstrating flying via Microsoft Flight Simulator is the Aircraft Owners and Pilots Association "PATH to Aviation" materials that are found on their website> (i.e. http://www.aopa.org/path/path.html). Also, from this website, plastic pilot wings can be obtained to give the students after completing a “flight”.   Finally, the ground school lessons that are included with Microsoft Flight Simulator are a good way to for students to learn more about flying.
Another good reason for having this flight simulator available is that it also makes a good fill in project when there is time left over after completing another project or when only a few of students show up.