One of the things I find most valuable is the history of a thing. In virtually every organization I've worked with, history has been vital, but massively underappreciated. At the end of the day, organizations hemorrhage institutional knowledge -- they remember what decision was made, but not why. Often this is because they fail to appreciate the necessity of documentation and/or the importance of the reasoning behind the decision. Inevitably, they thrash through the same thought processes over and over again when they could be moving on to the next thing.
All of this is a way of saying that history is a reluctant teacher. It stands there in the corner, knowing the answers to many of your questions, but will only enlighten you if you ask. (Data is another reluctant teacher -- as many of our questions can be answered with data on hand if only we know how to ask, but that's another discussion entirely.)
