Minor NPCs can be defined fairly simply as well:

1. Name (this is no longer optional)
2. Purpose (what role do they fulfill in the setting)
3. Motivation (something they want or are dealing with that might have nothing to do with 1 and 2 -- this is what will give them the illusion of depth if a Player delves into the character a bit more -- having found depth, the player will sometimes even go looking for more and thus this Minor NPC becomes more important.