The quick answer is: take advantage of every opportunity to get multiple experiences in the theater as you can find. I'm sure you've heard the old joke. A tourist in New York City asks a native how to get to Carnegie Hall. The one-word answer is: practice! That's also the magic word for anyone who wants to become a theater director. Practice, practice, practice!
If you're a young teen, get yourself involved in high school plays. If you're not asked to direct, take any job you can get that contributes to the production of the play, musical or concert. It could be scut work, such as messenger, floor sweeper, costume maker or curtain puller. Whatever your job, keep your eyes and ears open so you'll be on your way of learning everything about the theater, and how your career plans fit in with it.
When you have the time, also get involved in community theater, and take on any job you can get at first. If you have the smarts and leadership ability, you'll soon be doing something in the director's discipline. Between semesters of high school, if you have the money to travel, seek out opportunities to join summer stock companies. The pay will likely be very low or none at all, but the experience with a professional troupe will be invaluable in your determination to become and theater director.
As in high school and community theater, you'll have do do work much less dignified than directing, but you'll have the opportunity to observe and work with pros in action. Another important aspect of your yearning to become a theater director is that you must be a take charge guy or gal. If you're a follower or shrinking violet, directing isn't for you. Learn that fact soon in your career, and if you take honest stock of your personality, talent and ability to handle actors, and you still realistically believe you can do the job, then go on to the next step. If not, its time to consider another line of work.
Orson Welles performed and directed the infamous "War of the Worlds" radio show at 22, and moved up to cinema greatness by doing the same on screen in "Citizen Kane" at age 25. Ron Howard directed several episodes of his TV hit, "Happy Days" at 21, and his first film, "Grand Theft Auto" at 23. However, unless you're a genuine young genius with similar talent and are already in demand in professional show business, the best route to the director's chair after high school is finding a college or university with a good theater school that offers studies in theater directing.
For English-speaking students,there are dozens of colleges and universities in the U.S., Canada, Australia, Ireland and England that offer courses in theater (or theatre). Of course, for others, the opportunities throughout the world are limitless. I'll give very brief notes about five American schools I consider among the best.
1. The New School for Drama in New York City offers a three-year graduate degree program for directors, playwrights and actors. The school, while very professional, is often in the media, at times for its extremely liberal political traditions and sometimes controversial faculty members, graduates and guest lecturers. If you don't share the same views, you probably wouldn't be happy there. However, John McCain spoke at graduation ceremonies there in 2006, facing all kinds of student demonstrations, of course. Both Hillary Clinton and Barack Obama have had some interesting connections at the school. The Bravo TV program "Inside the Actors Studio", with James Lipton, was filmed there for several years..
2. Juilliard is primarily known for its excellent music and dance education programs. Its newest area of student study, the drama division offers excellent courses in theater writing, performance and directing. A degree from the prestigious Juilliard School in New York can open doors that could never happen for someone who was the most talented student stage director in Podunk U.
3. The University of California in Los Angeles (UCLA) offers dozens of majors in its School of Theater, Film and Television, including stage directing. Some professionals rate this university the best in the nation, and not only for its excellent bachelor's and master's majors in directing and all the other film and theater arts. Its proximity to the Hollywood film and TV industry gives students exposure to well-known experts from the director's profession, as well as many on- and off-campus job and internship opportunities.
4. The University of Southern California in downtown Los Angeles offers a significant major in directing, as well as many other show business courses. As with the other big city university, UCLA, its location and prestige attracts many to its faculty who are recognized directors in stage, TV and movies. Additionally, students have excellent opportunities to seek out part-time jobs and internships in the nearby show business industry.
5. I must add the University of the Arts in Philadelphia, particularly for bachelor's and master's studies in stage and film theater arts disciplines at its College of Media and Communication. I could be a bit prejudiced, because many years ago I earned my BFA in graphic design at the university, when it was called the Philadelphia Museum College of Art. At that time, there was no area of theater study, and those who sought master's in similar disciplines completed them at the University of Pennsyvlania.
However, the university's neighbor on South Broad Street is the historic Shubert Theater, and two blocks up the street is the famed Academy of Music. Then as now, there are ample opportunities for students to volunteer and enroll in internship programs that greatly add to their theater education.