Choosing Users to Test, and Preparing Them

The best test users are people who are representative of the people who will be the (real) users of the final system.
It may be difficult to find volunteers, especially if your future users are managers, doctors, lawyers, ... But if they are not willing to test a prototype, how certain are you they will be willing to use the final product?
Sometimes it may be possible to approximate the real users by means of students (in the right field).

Users need to be prepared before participating in a test: