There are several ways to get stage time. As a comic, I spent a dozen years honing my craft and got on stage about 1000 times doing standup comedy at open mics, showcases, road gigs, clubs, etc. There are so many opportunities to get stage time. Some are more appealing than others. The more polished your work is, the more likely it is you can get on “better” stages.
Open mics are at the bottom of the ladder in one way, because the audience is usually not paying and has little invested in paying attention. In another way, they are the best place to be when you start out because you can literally try anything. You have complete freedom to express yourself. There’s no one to please but your own internalized concepts of who you’re supposed to please. No one is paying you, so no one can revoke your paycheck. No one is hiring you, so no one can tell you they won’t book you again. And likely no one you know is even there in the audience, unless you’ve invited them. It can be an experience of real freedom. Another aspect of performing at an open mic is that the audience can be so hard to please, hard to snag, hard to capture, that any audience after that can seem dreamy. You might get heckled or interrupted, you might only have 5 minutes, you might have no one laugh (assuming your doing comedy), and you learn that you can live through it. Any improvement from there is magical.
One trap at open mics is that the only consistent audience always there are other performers. They can become the group of people you unconsciously start to try to please. The problem with that is they have extremely different sensibilities from other people, and when you arrive at a “normal” stage with a “normal” audience, you may find your material doesn’t fly at all. You may have become “too hip for the room”. Be ware!
A great thing to do is to find your “tribe”. When you’ve got some material to try out, go to places where “your people” are. If you’re a lesbian comic monologist, go to where those people are to strengthen your material. If you’re a straight white male, go to the venues where those people are and do your material there. Once you start to feel some clarity about your people and your voice, go to venues where other kinds of people are in order to strengthen your work and your appeal in new ways. Practice being yourself while communicating with people who are different from you. This is an advanced move though.
When you’ve got some material to work with that you’re happy with, look for the local venues that have featured performers, whether they’re solo performance nights, comedy shows, or poetry slams. Go check the show out. Meet the performers and the producers. Ask if you can get in the lineup!