First you’ll need to find out if there are any movies filming in your town, then you’ll need to call them to find out about casting calls for extras. Often there will be a separate telephone number for extras casting, and there will only be a recording on the other end of the phone. DON’T try to call the main number back and pester the person answering the phone because the word will spread that you’re a nuisance and you’ll never work in this town again.