Base Attire

• Most people own at least some black clothes.Photos.com/PhotoObjects.net/Getty Images
  
  Begin your ninja outfit with base attire, the fashion foundation upon which you will construct your ninja outfit. Ninjas were famous for their stealth and their nontraditional combat tactics like night attacks and sneak attacks (in contrast to the codified conduct of the samurai). Night-attacking ninjas presumably wore black for camouflage reasons and are usually depicted that way in pop culture. Don a pair of loose-fitting black cotton pants, such as black pajamas or karate pants dyed black, and a black shirt. Black bedroom slippers would work well as sneak-friendly, ninja-approved shoes.
  
  

Ninja Hood

• A black hood can suffice for headwear.Comstock/Comstock/Getty Images
  
  Disguise your face with a hood and a mask. For the hood, you can simply wear a black hooded sweatshirt with the hood up as part of your ninja outfit. The mask is slightly more complex. Obtain a length of black fabric -- perhaps a scarf -- that is long enough to go all the way around your head with length to spare. Arrange the fabric widthwise across your face, covering your nose and mouth to just above the chin and just below the eyes. Tie it in the back. Now you resemble a ninja and cannot be identified.
  
  

Outfit Accents

• Add accents to your ninja outfit if you have the interest, resources and time to spare. For example, you could keep the folds of your shirt close to your body (minimizing the risk of them catching on something and making noise that would alert your victim) by tying a belt around your waist. While all-black accessories would probably reflect ninja reality, you may wish to pick belts and other accessories in a contrasting color to add visual interest to your outfit.
  
  

Weapon

• A fake sword could work as a ninja weapon.Hemera Technologies/PhotoObjects.net/Getty Images
  
  Complete your ninja outfit by obtaining a fake ninja weapon, such as a dagger, a set of throwing stars, a sword or a pair of nunchaku (nunchucks). Depending upon your plans for what you will do when wearing the ninja outfit, you may or may not be permitted to carry the fake weapon with you. Many public events like parades and festivals disapprove of weapons, even artificial ones, so check with the relevant authorities about their fake-weapons policy if you plan to make a public appearance as a ninja.