Final answer:
The primary method used to restart the game after the ball goes out of bounds in soccer is the throw-in.
Step-by-step explanation:
The primary method used to restart the game after the ball goes out of bounds in soccer is the throw-in. When the ball goes out of bounds, the team that did not touch the ball last is awarded a throw-in. One of the players from the opposing team stands on the touchline and throws the ball back into play using both hands while both feet remain on the ground.