Hi all im some what new to learning martial arts, and i havent got passed white belt in Tai Qon Do since when i was about 10 years old. (at the time i wasnt very interested) Now im 21 and im motivated and interested in learning something for self-defense. Any ways to the point my question is do all specifc martial arts instructors teach the same exact techniques (like are the techniques written in stone?) For example do all differnt Krav Maga instructors (even if some instructors teaching methods are better than others), do they still teach the same principles and skill sets? I want to learn either Krav Maga or Ninjutsu, but dont know if i get the "not the best of instructors", then will everything they teach be useless? Or can I still pick up useful concepts,moves and principals that would be the same across varying skilled instructors?