Get yourself an agent, audition a lot, read plays, and by all means, see lots of theatre. Seeing theatre is one of the best ways to learn. Acting truly is a wonderful profession. If you are willing to work hard and are prepared for the reality that it is a very difficult life, and that you may never make a living from it, you can have quite a wonderful, fulfilling life. Being an actor means, among other things, touching part of the world that most people never get the chance to see.
Actors get to play, to dream, and to have a chance at changing the world one audience at a time.