Summarize this article in one sentence.
Jiu jitsu is a great foundation to martial arts practice because the fighting style relies on balance.  Much of the jiu jitsu takes your opponent's strength and uses it against them. If you belong to a Jujutsu school, you'll begin with the elementary throws and grapples. One of the first skills you learn is to relax during training. This enables you to train longer without becoming exhausted and also is good preparation to becoming a ninja. The core of Jujutsu is fighting without weapons. Some larger cities have ninjutsu schools that are open for willing patrons. This is the best way to learn the true techniques a of ninja’s fighting style. The core idea of ninjutsu is stealth. A modern fictitious ninja who incorporates this fighting style is Batman. Although knowing a traditional Japanese style of fighting is preferred, receiving any type of martial art training will help. You can always adapt the ways of your martial arts style into a stealth based style. You can also seek out further training after receiving a basic martial arts training.

Summary:
Learn Jiu jitsu. Discover ninjutsu organizations. Learn from a trainer.