If you want to be an extra on a film do you have to be with an agency and if so is there any other ways of becoming an extra?
Anyone can be an extra in Film and Television.
Unlike actors, extras do NOT have agents who take a 10 percent commission. You simply register with extras casting companies and call in each day on their casting lines to get work. Unless you hire a "booking Service" for about $30 -$50 a month to "call-in" and get you the work. Of course these "calling or booking services" really do not "call-in" to get you the work, they simply know people at the extras casting companies and get lists of what they need, and act as "sub-casting agents". Think about it, why would the extras casting company individually call each and every person, when they can just call a "booking service" and say, "we need 120 people for a party scene". Then the "booking service" does all the work and calls each of their clients themselves! SAG is trying to regulate these companies at some point, but the fact remains that these services can get you much more work than you can on your own just calling in on the casting lines all day trying to get through the busy signals.
The Screen Actors Guild does have jurisdiction over backround actors, however, the contracts only require a small number of union extras to be hired for a given union production, and the rest of the extras are non-union. This is part of the contract that production companies sign with the union. There is a publication called "Extra Work for Brain Surgeons". It truly is the Bible of Extra work. I am NOT one to try to sell books for anyone. But I am in the know about this subject.
Central Casting is the largest extras casting company in the world. (all of the info needed to register is on the site):
followed by Bill Dance Casting. You simply register with these places, and then you work. There is a huge amount of work for non-union extras, and just a small amount of union extra work. As a matter of fact, one can work every day as a non-union extra, but if you are a SAG member, it is much harder to get union extra jobs. This is because a given TV show for example, only has to hire 10 union extras, and the rest can be non-union. If you sign up with a "booking service" or "calling service" as they like to call themselves, you can literally work every day. But the pay is not much more than minimum wage for non-union, although overtime is usually the norm as well as "wardrobe allowance" and sometimes "mileage allowance". You also can get paid extra for using your car, pet, or props in a scene. There are many SAG members secretly doing non-union extra work simply because there just is not enough union extra jobs to go around.
You must live in LA (or within driving distance) of course, get a "Thomas Guide" map book, and have a cell phone and a car. But if you do your homework, you literally can work every day, no matter your experience or looks. You can be young or old, tall or short, overweight or underweight, some one-armed dude, or whatever. There is plenty of work to go around, and Hollywood needs all types of people. You don't even need headshots or a resume, they take a digital photo when you register with all of those extras casting companies. Just stick with the legit companies. There is a nominal $25 or so fee to register. Even SAG member have to pay a "photo fee" to register.
So there it is.
Don't take bad advice. Just register with the big extras casting companies and follow the rules of working as a fim/tv extra. As I said, I am NOT out to sell that book, you can do some research and find out all you need, but be careful as there are tons of bottom-feeders scamming people who want to work in film/tv as extras.
If you are lucky, you can even become "SAG Eligible" from doing non-union extra work, but that is a whole other long story.
Here is a link to HollywoodOS (the company that publishes that book "Extra Work For Brain Surgeons").
PS AFTRA (American Federation of Television and Radio Artists) has jurisdiction over Soaps and Sitcoms among other videotaped and radio broadcast productions. This is a whole different story, and anyone can walk into AFTRA and join for about $1,250