I am a Game Master who has been running session zeroes for years and I have a process that I like to go through; however, I am always learning new things, reading about new best practices, and trying to improve all my sessions. In my opinion, session zero is the most important session as it either consciously or subconsciously drafts up a social contract, gives the players a roadmap of the campaign, and gives players and the GM the opportunity to discuss the hard and soft limits of any content they wish to experience within the campaign.