How do callers get to appear on Car Talk?

This is what I believe happens, forgot how I learned it.

  1. you call and tell them your story
  2. they screen the call and determine if it is something they want on the show based on the problem and the entertainment value of the caller and other factors.
  3. if chosen they call you back to tell you to stick by the phone at a certain time.
  4. they call during the show if they have time.