Anyway, as with anything I approached the books with the eyes of a DM and I found some simplifications Martin adopted to help him tell his stories that might also help DMs trying to run players in a big, imagined world. Some simplifications you might consider for your fantasy world:
- Simple Family Names - There are some allegiances in the books that are complicated by marriage, but most are related to your immediate family and families in the books are clear because they have the same last name. Bastards are also clearly marked by a traditional last name, and marked in such a way that you know where their family is from (Snow, Rivers). This allows you to have a lot more characters floating about with out losing track of where they are from and where their allegiances most likely lie. (Many, though not all, of the place names in the books function in similarly simple ways: Oldtown, King's Landing, Winterfell, Riverrun).
- Simple Coats of Arms - Along the same lines, heraldry is simple and almost always utilizes an object appropriate to the location and vocation of that family. And soldiers wear badges of these arms. So you can usually tell just by looking who different troops belong to. That's the point of heraldry, but in real life it is much more complicated. I think that for many of the arms of Westeros players might even be able to guess where the family hails from without former knowledge.
- Simple Long Range Communication - Ravens - By sending message via the ravens, word of deaths and crimes can spread relatively quickly. And while uncertainty of arrival is always mentioned as a possibility, it's never been a plot point in what I've read so far. So, in effect, the castles become points of civilization where news is heard and only someone traveling between them won't be privy to important goings on. Individuals can also send messages, using the ravens like a mail system. This means you don't have to have a complicated system to track the spread of news based on travel times of merchants or peasants, just have ravens carry the news and get on with the show.
- Assumed Knowledge NPCs - Maesters - Every castle has a source of history, technology, and healing. And because of their vows, these maesters while serving that family, are generally neutral and not seeking power or wealth of their own. Have a wound or question about historic lore-- head for a castle. Priests are a similar resource, a septa or septon in every castle, but because of the low magic beginning of the series, they are less important in the books. It might be more important in your world that every castle has a chapel and a priest.
- Assumed Dumping spot for troublesome NPCs - The Night Watch - It seems a neutral faction with its own military but concerns other than ruling, might be handy for many reasons. Having an order to put criminals or potential threats to succession in means these threats never disappear, can be questioned by players, and can become threats again if they break their vows. Also, the faction can be a place for players to look for aid, if it aligns with the order's goals.
Anything you would add?