From publisher blurb:
What does it take to create a living, breathing world? GMs and DMs often spend a great deal of time trying to capture and project a certain feel for their games. Mood, setting, depth of character and history - all of these things are necessary for a truly vibrant fantasy world. This might look like a lot of work, and sometimes it is - but for enterprising GMs/DMs, much of the illusion can be achieved through the creation of realistic, well-thought out, and believable NPCs.
The keys to creating such NPCs are memorable descriptions, vibrant personalities, and personal motivations and goals. Pick and choose which of these listed details you want to use, and breathe life into even your simplest encounters. Give a splash of color to every burly village blacksmith, gruff town merchant, and evil, despotic villain in your campaign.
The following list will help to provide you with the right tools to get that done, from deciding the NPC's general mannerisms to fleshing out their history and secrets to figuring out how they are connected to the other NPCs and organizations in your campaign world.