Last night's rehearsal was dedicated to what we in the business call table work. This usually involves the director or dramaturge (fancy work for person who researches a play) will throw lots of sheets of paper at you. Then the actors will scramble home with said papers and read them over so they can invest the character with at least a passing knowledge of what all those words they are saying really mean. The fact of the matter is you have to do your research but sometimes you can get so caught up in the details that you forget that there is a human being living inside of those lines.
Here is what I do to avoid the pitfalls of too much information. I learn everything I can about the character I am playing and how they fit into the world around them and then I leave all the rest to the directors and designers. It has always been my opinion that most characters only know the facts and events that impact their lives directly. Just because I am playing a samurai in Heian Japan, doesn't mean that I have to know the inner workings of the agricultural system of Japan at that time. I need to know how to be a samurai and what my role in society would have been, not how high my kimono would have been cut.
Here are some web sites I have found about Samurai History and Culture:
Samurai Archive - Has a lot of information on history and tradition, as well as an extensive listing of names and poetry.
Japan.com - Has a simple timeline of the history of Samurai in Japan.
Wikipedia - As always supplies an easy to read and illustrated overview of Samurai tradition and as with all things Wikipedia some of the weird stuff too.
Nobuji's Unofficial Akira Kurosawa Fan Page - Just for the pop culture that we all need this site looks at all of the films of Kurosawa, including the Seven Samurai, Throne of Blood and Ran.