So, the stealth techniques in Ninjutsu are primarily born out of your ability to do Tijitsu movement in an accomplished way. And again, it goes back to your basics.
Being able to walk correctly, stand correctly, and if you can do those things well, then you'll understand the body dynamics and movements that's needed for moving quietly through really any environment. That type of, developing that type of body awareness is really key in the stealth movements of Ninjutsu. Really, one way to approach that type of training is just exploring different environments that you may happen upon.
And exploring how to move efficiently through those places in a way that feeds you in a way and gives you more experience and body awareness. So, as you're moving through a different environment, it's also important to be aware of not only the environment but the types of people there, whether they're people or animals or what have you, and to be aware of what their concerns are and what their thinking is. Really people are apart of the environment.
So essentially, you just have to be one with whatever is there, and that will help you have a greater understanding of an idea about how to perform stealthy movement through an environment.