Although I haven't worked as a talent agent in over a decade, people still ask me: "How can I get an agent?" My response remains the same, "You don't get an agent, an agent finds you."
Getting an agent is how I imagine dating was back in the 1950s. A girl does all she can to make herself attractive to a boy (pretty hair, a little lipstick, pressed clothes, good manners etc.). Boys will notice her and start to chase. She may get a boy who is interested in asking her to prom or she may even have a few suitors for the big day. Either way, she is then in the position of power to say "yes" to one of them. Sure, there is an occasional "Sadie Hawkins dance" or "Girls Choice" but the general rule is that the boy does the asking.
Same is true for getting an agent. If you are a writer, director, producer or actor and want CAA, WME, UTA, ICM, Gersh, APA, or Paradigm to pay attention to you, then pay attention to this:
Hollywood is akin to a 1950s prom: The Artist is the girl and the Agent is the boy. An artist needs to be as attractive as possible to an agent. That means the artist needs to WORK!
If you are a writer, write. If you are a director, direct. You get the idea. Get your own jobs. When you are good, trust me, an agent will notice you and ask you to become a client (or at least take a meeting.) Most agencies have certain criteria that need to be met before they will sign you. It might be an annual dollar amount, it might be a certain number of social media followers, or it might be that an entire department of agents need to reach a consensus before signing you. Regardless, you need to demonstrate sufficient earning potential or a track record that shows solid growth.
Think about it this way, an agent gets 10% of what you make, so if you aren't making much, you aren't attractive to an agent yet. It isn't anything personal, but they want to see how the market responds to you first before they invest time and energy behind you. So, start working as a production assistant, writer's assistant, production company assistant or anything that puts you in the environment to do excellent work.