What should a referee do to indicate a substitution when a team is ready?

To indicate a substitution when a team is ready, the proper signal is to rotate the arms at shoulder height. This gesture is clearly understood by players, coaches, and spectators as it communicates the intent to allow a substitution. The referee's action must be visible and unambiguous, ensuring that everyone on the court is aware that a substitution is being made.

Using a sign that involves clear arm motion, such as the rotation of the arms, effectively indicates to everyone involved that the game is temporarily paused for the purpose of allowing a player to enter or exit the game. This is crucial for maintaining the flow of the match and ensuring that the game adheres to proper officiating protocols.