With all of this in consideration, the first approval comes from the IOC Executive Board, who, once they have approved a petition, pass it onto the rest of the IOC. Then, suddenly, you're watching Olympic golf on a Thursday afternoon in August, more or less.
It's not actually all that sudden. Golf and rugby were approved for inclusion back in 2009, seven years in advance of Rio. That's the typical time frame for a sport to make it's debut when approved through the traditional route.
Additionally, any time a sport is added it is not considered to be permanent. Golf and rugby are only set for inclusion at the 2016 Games and the 2020 Games. Following Tokyo, both sports will be reviewed to determine if they'll continue to be a part of the Olympics.