One of the most useful new concepts in IHW:SC and SC3 is Cultural Traits. Each world has its own culture, and each culture has traits. The culture from Rienhart's World might be Aggressive 2, Subtle 3, Arrogant 1, and Impatient 1. This group of traits, then, represents a caricature of a person from Rienhart's World. Individuals, of course, may vary widely from this caricature. They may in fact exhibit none of these traits, but on a bell curve, these traits stand out as most representative of this culture.
This gives the Player and GM both a baseline to construct a character, NPC or PC. Rather than working cold, one can take the baseline as the default, then decide if and how the individual deviates from it. It not only helps constructing the character's personality, but also gives an indication of how that character fits into that culture. Someone with slight variations should have little problems, but someone with large differences, especially oppositional differences, might be very out of place.