How do I pursue a career in acting (stage and film).?

Well, first you need to have a experience on stage. Try to do a play ASAP. You need to see if drama is your thing. Then, you need to do training and acting/singing lessons. You should learn how to dance too, so you can be a "triple threat" and agents and casting directors like that. You should also do headshots for your agent to send over to casting directors. Don't worry I don't think it doesn't need to be professional.