Three followers hint
Get a contract follower (for example, Fawks, Charon, Jericho, etc.) and travel to the Scrapyard to get Dogmeat. Once completed, activate the "Stealing Independence" quest and soon as you enter the building, speak to the girl named Sydney. You can get her to follow you for the quest. You can complete it but cannot get her to follow you again. You should have three current followers.