How do people get more efficient at getting headshots? And how do they know (roughly or precisely) at what hight to aim in order to maximise the chance of getting headshots? I've been trying to use objects in the map (which I've read is how...

Yesterday during an unrated match, my wife and I were getting stumped by the enemy Jett. She was wide-swing-one-tapping us and clearing corners like a well-trained K9. She had 20+ kills by the time we switched side. She even taunted us in t...