1st - Ninja's are silent; hence, ninjas must limit themselves to silenced weapons only
2nd - Ninja's are silent; hence, ninjas must only make noise when absolutely necessary, i.e. walk and crawl for most movement
3rd - Ninja's are at home in the dark; hence, ninjas must wear darker uniforms
4th - Ninja's are at home in the dark; hence, ninjas must always carry nightvision
5th - Ninja's may use smoke and flash grenades in order to escape detection, or "ninjavanish"