These questions plague the aspiring actor. Whether he or she has just decided that acting is what they want to do or whether her or she has just graduated from college or conservatory, what to do next is the main quesition. Of course if schools did a decent job of educating aspiring actors, they would know what to do when they graduated. But too often, the schools don't do that. Let's start with the beginner. For this person, the answer to Where to is nowhere if you have access to school or community theatre. And the Answer to What Next is to get some acting roles in plays on your resume. This could take a while, even years, so don't get in a rush to become the next star. First you have to have some evidence that you can act. That would be your resume. And the roles on it had better be good ones that demonstrate that you have extra ordinary talent. If they don't, then you might as well consider acting as a hobby or recreation in community theatres.
If you are just out of high school with a good resume, then off you go to seek your fortune as an actor. Unless, of course, you are too immature to support yourself and have to rely on your parents and do their bidding and go to college to learn a sensible trade. How to obey them and stll pursue acting is covered in my book, The Tao of Acting, free e-version is available at email@example.com. That also will help you build your resume a bit. Finally if you are one of the people whom education has failed, you need to read The Tao of Acting to fill in the blanks. Now let's see. Where to? What Next? Simple. Where the action is, and not LA nor NYC necessarily. And what next, start getting your tools together to run the business of being an actor.