The best way to get starteed is to be on set. But, there are ways better than others in learning. At your age (and you're not too late at all. You're actually the perfect age to start), look for professional video and film productions around. If you are going to film school, don't plan on getting to direct your first time out. In fact, I would recommend against that.
Instead, find people at your local film school who are more focused on specific areas such as screenwriting, in cinematography, in production design, in grip work, in camera department, in sound department, in production (for assistant directors, producers, and production managers). Ask them if you can come work for them, and you will learn each different department that works on a film and television set.
Once you have learned the nuances of the entire film process, you will have not only a better respect for all the people that are required to make a great film, but you will also learn techniques and foster ideas on how you want to direct your movies. It will give you a more rounded view of film instead of the vision that you originally wanted to create, and your projects will be unique and exciting, more so than your other colleagues who wanted to be directors, and only worked toward that goal.
