Pick a t-shirt that you know other ninja will not bother you about. I chose a "Clerks" t-shirt.
Step Two
Turn the shirt inside-out and put over your head normally, but with the tag down (backwards) and hold the sleeves out to the sides.
Step Three
Tie the sleeves in a single knot in the middle of your head. Very simple. Pull it tight so the mask does not come loose during battle.
Step Four
It should look like this with the tag down under your nose. Very soon, ninja you will be.
Step Five
Pull the top collar down your forehead and fold it up. Keep the facial space to a minimum and pull it right to your brow.
Step Six
Pull the bottom collar and tag up over your nose and fold it under the same as you did with the top collar. You will find the sides will fold into each other very nicely.
Step Seven
Find yourself an interesting, yet threatening ninja pose. As a ninja you obtain certain responsibilities such as kicking asses and looking cool and tough.
CONGRATS / Finish !
You are now a SHIRT NINJA! Now go forth and kick some ass!