When you make many, many characters, and your first move after making the character is to go to the commodity dealer to sell the rules and history for 200 credits, you notice NPC's with a $ logo above their head.
Comes with time and repetition, I think. (Like the trade-lane stuff.)
When I was debugging the Vespucci system for 4.85 (current version), I had to remove an Outcast NPC that was hiding in a corner of the ship dealer room on Fort Leniex. No, I'm not kidding. It managed to sneak in somehow when the system creator wasn't looking.