Train to Be Ninja Using Stuff You Find at Home

Training to be a ninja will be hard but satisfying and you can begin at almost any age. Most of people start been a ninja with 15 years old

Steps

Build up your strength and flexibility. Pull-ups and pushups are a good workout for the arms, squats work the leg muscles and crunches will work your core.
Become-Flexible. Flexibility is essential for a ninja. Practice stretches such as the straddle, pike, and butterfly stretch. Remember to warm up before stretching.
Learn how to fight. The best way to do this is by learning a martial art. Ninjutsu is the obvious choice, but since good schools are uncommon, you may not be able to learn it. Martial arts such as Wing Chun, Jiu-jitsu, Taekwondo, or Hapkido will also work.
Build endurance. Run, jog or swim for a cardiovascular workout.
Practice hourly every day and drink plenty of water.
Learn Parkour to increase your agility in urban environments.
Keep the fat off!
Train your mind as well as your body.

Climb trees, do pull-ups on the monkey bars, and practice stealth and blending in.
Ask a friend to battle with you to see how much you have progressed. Be sure to go easy on them; you do not want to hurt your friend!
Believe in yourself
Tell no one you are a ninja
You can also make your own tools. Buy things like paracord and use strong metal hooks to grapple up walls etc. Make them light and small but still usable.
Always be prepared, bring a bag with your tools everywhere. Flashlights, lighters, simple food etc.
Go online. There are plenty of ninja resources on the Internet, but be wary of false information.
Start off with about 5-10 push ups. Then work your way to 50 or 100.
Wear dark clothing, and move stealthily and quietly.
Make sure you don't hurt anyone innocent and remember no one is really your enemy.

Do not use your skills to harm anyone unless you need to.
Try not to get into trouble training or being a ninja. Stay clear of the law, teachers, and maybe your parents.
Make sure you will not damage yourself or anything while training.