How can I become a Spartan?

I'm curious, how exactly does one become a Spartan? I understand it's a prestigious title with a rich history, but what specific steps or requirements must be met to achieve this status? Is it through rigorous training, a certain level of physical fitness, or perhaps a demonstration of bravery and courage? I'm eager to learn more about this prestigious path and what it takes to earn the title of a Spartan.