What must a player do before lifting a ball in play?

Before lifting a ball in play, it is essential for a player to mark the spot of the ball. This action is crucial because it allows the player to replace the ball in the exact spot from which it was lifted once they are finished with whatever action necessitated the lift. Marking the spot ensures that the integrity of the game is maintained, as even slightly moving the ball can inadvertently change its lie or its relation to other elements of the course.

Without marking the spot, the player risks losing track of the original position, which can lead to potential penalties or disputes regarding the placement of the ball. This process is part of the Rules of Golf, which emphasize the importance of maintaining the ball's position to uphold fair play.

The other options, while relevant in different contexts, do not encompass the necessary procedure that must be followed prior to lifting a ball. Notifying the opponent is generally related to certain situations but is not a requirement in all instances when lifting a ball. Taking a practice swing and assessing the lie, while helpful for a player's preparation, do not address the fundamental requirement of marking the ball's position.