One card (Power Play) states that its controller is the starting player. This effect applies after this determination has happened and supersedes these methods.
April 17, 2020 · Ikoria
In a Commander game, each player puts their commander from their deck face up into the command zone after having the opportunity to reveal a card with a companion ability and before shuffling. See rule 903.6.
April 27, 2018 · Dominaria
In a Conspiracy Draft game, each player puts any number of conspiracy cards from their sideboard into the command zone before shuffling. See rule 905.4.
June 1, 2014 · Conspiracy
In a Conspiracy Draft game, each player puts any number of conspiracy cards from his or her sideboard into the command zone before shuffling. See rule 905.4.