The best way is, of course, to read the books. We prefer all players to have read at least A Game of Thrones.
But even if you have read all the books, keeping all the information about the series fresh in your mind is easier said than done. The Citadel is the section of Westeros where we have collected setting-related resources, such as the Concordance, which is a compilation of just about every little piece of setting information from the series made specifically with this MUSH in mind.
You can also find a lot of information about the setting in our wiki and at our forum. However, keep in mind that those sections contain a lot of spoilers and that not all that information there has been checked for accuracy by the Admin.