Sometimes I'll hear a phrase or a word and write it down in my little black notebook (a writer's best mate), then come back to it and work a plot around it.
“Our constitutional liberties shall not be sacrificed in our search for greater security, for that is what our enemies and all enemies of freedom and democracy hope to achieve.”
“I met my wife by breaking two of my rules: never date a girl seriously that you meet at a nightclub and never date a fan.”