Ninjas and the art of Ninjitsu are perhaps the epitome of martial arts at their best. While there is a large cloud of myth surrounding the ninja you can find schools and classes that will teach you ninjitsu around the globe. Of course there are less of these types of schools than the standard martial arts school like; Taekwondo, Karate and Kung Fu. Since these are schools are few and far between this certainly adds to their mystique. You can even find quality ninjitsu home study courses on the internet.
Besides their stealth the ninja are best known for their expertise with specialty weapons. The ninja are know as using some of the coolest weapons in history and they are still popular today. However, besides technique and weapons training, the thing that separated the ninja from the rest was their basic training principles. To become a ninja you could have no fear and you could not recognize pain. In fact when a ninja went into battle there probably wasn't much an opponent could do to them that hadn't already been done. Going into battle, not only armed with the great skills of the ninja but truly without fear makes for an incredibly fearsome opponent that can likely only be stopped with a fatality. This combination of qualities created a truly unique assassin lethal machine.
If you are looking to getting involved in ninjitsu training you will need to see what style the school trains in. There are several 'styles' of ninjitsu and a lot of schools are just a watered down Karate or Taekwondo class but, nothing to do with actual ninjitsu. One great person to follow in learning about ninjitsu is Stephen K. Hayes. He has been in the ninjitsu spotlight since the 80's and has written numerous books on subjects like stealth, defense, and weapons. This type of training can take a lot of time since it has to include so many different facets, but luckily if you practice the basics they always remain and stay the same.
Today it is sad to see many martial arts classes. Students are whining and wimping out saying things like "I am too tired". You certainly would not have dared to question your instructor or complain if you were training under a real ninja master would you? This does not mean you have to punish your body to a pulp however, you just need to put all your heart and soul into your training. If you really want to bring it like a ninja it all begins with your core training and building both mental and physical toughness. Train harder, train longer and never give up.