|Pathfinder Face cards or similar NPC artwork|
can help imprint NPCs into your players' memories
In a vibrant campaign, the potential should be there for the party to create a relationship with any NPC met along the way. Often times, the most surprising role playing can come out of a chance meeting with a random NPC.
There are a couple quick and dirty tricks I use which I call the “Quick & Dirty NPC Generator”. It's basically a sheet of paper with some notes to have nearby during your sessions. Here's how it works.