In a nutshell, historiography is the history of history. Rather than subjecting actual events - say, Hitler's annexation of Austria - to historical analysis, the subject of historiography is the history of the history of the event: the way it has been written, the sometimes conflicting objectives pursued by those writing on it over time, and the way in which such factors shape our understanding of the actual event at stake, and of the nature of history itself.
Questions of historiography include the following:
As you can tell, the underlying sentiment of historiography is one of skepticism. This is due to the recognition that historians do have agendas and do select sources with the intent of "proving" certain preconceived notions. History is therefore never truly "objective," but always a construct that presents the historian's view of things. At its most objective - and even this is debatable - history presents basic "facts" (dates, events, etc.); the task of the historian, then, is to interpret those facts, the outcome of which (a book, a journal article, a lecture -- even a student paper) can never be truly objective, as interpretation is by definition a subjective mental process.
All this is just a fancy way of saying what you already know, and what has long been articulated in such platitudes as "the victors write the history." Does this render the entire pursuit of history pointless? Do not despair: far from undermining your desire and potential to become a better writer and student of history, a keen sense of historiography will in fact increase your potential in these realms. Asking the types of questions bulleted above of any historical text you read will push you to delve more deeply into the matter, to explore both the event itself and the writer whose work you are reading in greater detail, and to consult additional sources. The outcome may complicate your view of things but, undoubtedly, will give you a greater appreciation for the many factors that contribute to the interpretation of an historical event, including factors of bias and prejudice - even your own. This appreciation, in turn, will make you a more thoughtful reader and writer of history yourself.
For the most part, historiography is simply something to keep in the back of your mind when you read a text or sift through your various sources as you prepare to write. Occasionally, a historiographical insight is worth a footnote, or perhaps even an aside in the main text of your paper (in which case it will already have had an impact upon, and will have raised the quality of your thinking and writing on history). Sometimes, however, a grasp of historiography can be the very point of an assignment. For tips on how to write a historiographic essay, click here.