Parkour (occasionally referred to as free running by xenophobes who hate the French) is quite possibly the most awesome way of getting around ever imagined. Invented by someone with an efficiency complex and a flair for the dramatic, the goal is to get from point A to point B by covering as little ground as possible. Any obstacle in one's path is to be conquored by jumping and climbing over it in a stylish manner. But it is by no means a spectator sport, making it perfect for ninjas, who are known for their dislike of being observed while going about their ninja business.
And so we come to the "How To" part. First, you need to be unbelievably awesome. Seriously. This takes physical and mental preparation, the weak of heart and body can easily cause permanent damage to themselves. Second, you have to be just the right ammount of stupidly reckless. Not stupid or reckless enough and you may hesitate at the last moment, lose momentum, and hurt yourself. Too stupid and reckless and you'll probably win a Darwin Award at your funeral. Just warning you.
Forget the rest of the stuff, you really just need to be able to fall without hurting yourself and maintain momentum. Being good at problem solving doesn't hurt either since the goal is to navigate an obstacle course of fences and buildings and other objects while running at top speed. You need to think fast and suspend your belief in "dead ends". Just as martial arts trains you to fight your opponent, parkour trains you to chase them down. Pretty cool, eh?