Compose a list of the various movies being filmed in your area. The best way to do this is to call your state governor's office and consult its department of film and theater. This department will know which movies are being filmed and where. If you live in a large city, such as New York City or Los Angeles, you can contact the mayor's office for a list of films currently shooting in the city.
Find the addresses for the locations department of each film. You can easily do this by searching the Internet for the business site of each film.
Send a resume and a cover letter to each locations department. You'll want to apply for two jobs: locations production assistant, which involves on-set work, and locations coordinator, which involves office work. Both jobs are entry-level positions in the locations department. By building experience in these positions, you will become more desirable as a potential film scout.
Perform the tasks given to you in these entry-level jobs to the best of your abilities. The locations coordinator schedules the shoot dates for the various locations and makes sure the film staff knows when to shoot at a given location. The locations production assistant actually travels to the filming locations and prepares the given location for shooting.
Repeat this process after the film you worked on has completed. As time passes, you will develop contacts and learn about scouting. Eventually, you will be able to apply to locations departments as a film scout or even receive offers from departments.