There are many websites which are put up by various agencies and studios who are looking for Extras. Sometimes they post what seems to be an ad…
Looking for Men and Women to portray pedestrians in a Day timeNew York Street scene.
People will know, (such as those in the image) what is wanted. They’ll come to the casting, some carrying a briefcase, others shopping bags, and they’ll dress as average people going about their day.
In other cases there might be uniforms, such as busy police station, and there will be a wardrobe visit a few days before the show is filmed.
The dates will be posted so that you’ll know if you can’t get to the wardrobe at the place and time, you can’t be on the set.
Many want email images, some might want videos, some might want resumes.
If you don’t belong to any casting studio, this is how you do it.