This is a little idea I had for a way to evoke the kind of rich cultural texture I enjoy from fantasy and sci-fi games, without pages and pages of notes, histories, and pre-prepared NPCs. Here's the idea:
First, you need to come up with 13 "rules" for your culture. They should range from really broad, general, and non-intrusive, through to very specific, all-encompassing laws. You can crib them from existing cultures if you like. Depending on the game, maybe everyone can help come up with these. Number them 2-10, then Jack, Queen, King. For example:
2: People wear blue for mourning.
3: Women always get first choice of food, and the eldest choose first.
8: There is a tribe called the "Gazzir" who provide guards to aristocratic families. The tribe is reknowned for honour unto death, and fanatical loyalty to employers.
9: Swords are forbidden to be carried by anyone not of noble liniage. For this reason, pole arms are common.
Queen: Those who are sentanced to death, or contemplating suicide, can opt to join a sect of monks called "the Nameless". They give up their old identities, and live ascetic lives of servitude.
King: The Emperor's word is law, and none may question it and live.
Now, in game, when you need an off-the-cuff NPC, or if you're preparing NPCs for a game, draw a card. Referencing the number on the card, check the suit:
Hearts: The character embodies, enacts, or enforces the rule.
Diamonds: The character twists, alters, or avoids the rule.
Spades: The character's life is altered (for good or bad) by the rule.
Clubs: The character breaks the rule.
So, drawing from the above list:
2 of Diamonds: Alaric the Mason wears blue every day, and has done for years. No one knows if he's mourning a long-dead wife, or if he's just weird. Though he seems perfectly normal in other respects, it makes people suspicious.
3 of Spades: Gwen is the mother of five hungry children, and poor. She lives with her mother-in-law, who always chooses the most food for herself, leaving very little for Gwen and the children. Gwen is forced to eat almost nothing, so her children can survive.
8 of Clubs: Numun the Betrayer was a Gazzir guard who betrayed his employer, a cruel and merciless man. Numun and a few of his friends slew the man. Now Numun's tribe is hunting him down to restor their honour.
9 of Hearts: Darran of Everwood is a young nobleman, and an expert swordsman. He itches for a chance to test his skill against the best in the land.
Queen of Diamonds: Aliea is an advisor to the Emperor. Though she wears the garb of the Nameless, and claims none of her former identity, forgoing even her name, she is often present at high-level meetings, and has a strong voice in the Emperor's war-council.
King of Spades: Beatrice, a serving-woman at the palace, is sentanced to death for refusing to go to the Emperor's bed.
Aces: Aces are a special case. Come up with a previously unknown rule, and then refer to the suit to find the character's relationship to the rule.
So the idea is that you get a whole lot of characters with kind of intertwined fates, different stakes in the culture. I think it's an interesting way of doing "show, don't tell" in a fantasy game, where the culture, and how it works day-to-day, is revealed by the characters the players meet, rather than dictated from on-high. If nothing else, it's a great prompt for imagination. These characters were all thought up on the fly as I was typing this, but I'd be happy to have any of them in my games. I like how they really act as plot-hooks, but they're plots that are firmly rooted in the culture. So often I think fantasy cultures are treated as this monolithic thing, where all members of the culture adhere to a set of guidelines unerringly. What I like about this idea is that it introduces the complexity and moral ambiguity of real cultures, without endless complications to the game.