No good soap opera would ever be complete without a dramatic scene with a slap. No good story about celebrities would ever be complete without some crazed fan screaming about having her idol's baby. And no good science fiction yarn would ever be complete without something with tentacles.
Hence the idea is to consider dependencies. I also will use a kind of (it's not the official 'snowflake method') starburst method where I will take a legal pad and write a major character's name (or what the character is if I don't have a name yet, e. g. the cab driver) and circle it. Just write it in the middle of the sheet.