I guess this question is as old as RPGs. Anyway, how do you solve this age-old dilemma?

I've come up with several possible scenarios:

1) Fresh off the boat. The good old scenario from the Empire of the Petal Throne. Its simple and fast and in many ways rather realistic -- players know as much as their characters and vice-versa. Later in the game, dead characters could be replaced by native Tsolyani. The main problem is the lack of any background when it comes to player characters. Yeah, we hail from the southern continent and so on. Why would anyone take these clanless weirdos seriously? Also, a huge portion of Tsolyani culture will be neglected if the players are outsiders.

2) As 1, but the players hail from neighbouring empires. Thus the players would have clans, a background and some informations to build on. On the other hand, they would probably worship Gods different from Tsolyani pantheon. Also, they would need to have at least some information about their homes -- so why not make Tsolyani characters and give them information about Tsolyanu? On the other hand, it is easier to tell players basics about their home that it is to give them all information necessary to survive in a given place. Player with a Mu'ugalavyani character needs not to know everything about his homeland -- it would be enough to know that the Mu'ugalavyani are warlike, efficient, serious and worship flame-gods. The player could take these as a base and then go on to explore Tsolyanu.

3) The player characters are Tsolyani youths. The game starts with a khatunjalim. This would need much longer briefing, but as the characters are youths they still might be rather oblivious. Players would have a clan, a religion, etc. On the downside this would probably lead to a lots of "you already know that..." situations which I don't like. The player characters would also be rather inexperienced, their education still being unfinished which would cut down character generation possibilities. This is especially true with sorcerers. I don't really think players would enjoy playing a character who spends most of his time at temple school.

4) As in 3, but the player characters can be of any age (preferably around 20). They hail from some remote part of the empire, being very ignorant about the ways of big cities. Perhaps every person in their home village belongs to the same clan so the etiquette has been less restrictive as all are clan-cousins. Players would have a clan and a religion and these would support them in their new home Katalal (or Jakalla or whatever).

5) The players are all Mihalli who are going to infiltrate the Tsolyani society. This is more of a thought-experiment than a real possibility, but it makes me smile so I decided to share it with you-

By the way, after re-considering option #3 I realised that it already offers roughly the same advantages as #4.

From what I've understood, the larger clans (especially wealthier ones) already have their own quarters in each city. The clan-house must be just a small portion of clan's real estate given the fact that an average clan probably has thousands of members in any given city. So I don't see why an average kid would have much experience of the world outside his home district. Of course they would know the basics but how much else? I come from a small town (2,500 pop) and when I moved into a city to study in a university it was terrifying experience! There were so many unwritten rules and things one ought to know!

Coming of age is always difficult and it must be difficult for young Tsolyani characters too! Actually, it would be very implausible if it was not. Basically, young Tsolyani adults should be experiencing the same shock as their players.

OK how about this. The players are all members of the same Clan and from Katala and you run High And Dry as the first adventure. So what you say. You start the game as they cross the river leaving Katala on the long walk to Mishabar. You can describe the farmlands as you go, pointing out similarities and strangeness as you go. How different will the wheat fields be from what they've seen, not much really. Oh look there is a Chlen cart. BTW that dinosaur-like creature over there is called a Tsi'il and is a food animal.
On the first night you describe the sky, always good for a WTF happened. They there will also be the odd wandering pest to annoy the party wit. Done right by they time they hit the module proper they should have the basic idea. That does assume they'll ask questions and wonder about what is going on, rather than passively sit there.