SHORT ANSWER: You don't. You can try acting at a non-professional level and that's a good way to star acting. But the acting business/professional acting is not interested in inexperience/untrained actors. Sorry.
LONG ANSWER: The only people in the acting business interested in experienced actors are...
Best answer: SHORT ANSWER: You don't. You can try acting at a non-professional level and that's a good way to star acting. But the acting business/professional acting is not interested in inexperience/untrained actors. Sorry.
LONG ANSWER: The only people in the acting business interested in experienced actors are the scams and rip-off who prey on naive wannabes who mistakenly think they can just be "discovered". Companies invest a lot of money in their productions and trust that investment to trained and experienced professionals. They don't hold open auditions that anyone can go to. For most professional work you have to be invited to audition, usually through an agent.
How professional casting works is this. The company hires a casting director (CD) to find qualified actors to audition. The CD writes a "breakdown" - a description of the project and the roles to be cast. These breakdowns are made available to talent agents, not to the general public. Agents review the breakdowns and submit the appropriate actors to audition. To submit means to send in an actor's professional headshot and resume listing their acting training, experience, special skills and links to a show reel demonstrating their previous screen work. If the CD is interested, they contact the agent to schedule an audition. And most professional productions in the US are union productions, which means preference will be give to actors who are members of the SAG-AFTRA actor's union.
You can't just hire an agent - it's more like they choose you. Legitimate agents are paid a percentage of what an actor makes - never pay an agent up front. Since they only make money if an actor books a professional job, they are VERY picky about who they take on a clients. They need actors who have demonstrated that they can work at a professional level through their training and experience. And you can't just join an actor's union. You need a specific type of experience to be eligible to join.
All of this is why you're not going to get into the acting business without any acting experience.
But don't give up hope! If you're interested in acting (instead of trying to find some quick way to fame) you should give it a try. Take some acting classes. Audition for things like community theater and student films. Find out if you really love the work of acting - auditioning, analyzing a script, building a character, memorizing lines and blocking, rehearsing, taking direction, working with a cast and crew, as well as performing. And see if you are exceptionally good at it. If you can't get cast in community theater or a student film it's not going to be any easier at a more professional level.
Once you have some training and experience, you can research the business end of acting. Understand the casting process, legal issues (contracts, taxes, unions, work permits and trust accounts for minors), marketing (headshots, resume, show reel, websites, social media, etc) and networking. It's show business, not a lottery. People are not just discovered off the street and given an acting career. A professional acting career is like starting and running a business where you are a product to be marketed and sold. You (or your parents if you're a minor) must be willing to step-up and take responsibility for any career you attempt.
3 days ago