I always enjoy watching arguments between players for taking penalties and free kicks. It seems like the manager would have laid out who was taking what freekick depending on the position on the pitch and the players on the field.
Craig Bellamy has a story about this in his new autobiography. Apparently Rafa would set the PK takers for each match. Well classic Bellamy wins a PK and then demands to take it. Whoever was designated for that match eventually let him have it. He converted.
After the match Rafa called him into his office and let him know he was being fined and wouldn't make the bench for the next match.
Not sure if all managers have a similar process or not.