Start off with the normal world – how was that day supposed to go? What was the player's goals before the inciting incident. Then start to think about how things could go wrong, or not according to plan
New information could spur the players to follow an adventure
Something might abruptly change the current way things are playing out. Possibly causing players to be fighting for their lives.
Attacked by someone/something, magic portal suddenly opens, wrongfully arrested,
It's always good to have a back up one of these, just in case players don't take an initial hook.
Think about characters that could throw a spanner in the works, or would be interesting and maybe draw players in
Think about making the catalyst experience assymetric for each player