To be a ninja, focus on developing essential skills such as agility, stealth, and discipline. Practice physical activities like martial arts or parkour to enhance your body control and movement. Additionally, learn to be observant and aware of your surroundings, which is crucial for stealth. Training your mind is equally important. Study strategic thinking and problem-solving techniques to improve your decision-making abilities. Incorporate meditation or mindfulness practices to sharpen your focus and mental clarity. By combining physical prowess with mental strength, you can embody the essence of a true ninja.