Why broadside is the textbook shot
Both lungs are exposed side by side, the heart sits low between them, and the bullet meets the least bone on the way in.
Wait for the leg
When the near front leg steps forward, the heart is uncovered. When it swings back, the shoulder blade covers more of the chest.
Typical miss
High and back. Hunters aim at the middle of the body, which is above the lungs and behind them on deep-chested game.