The study of historiography is about highlighting issues to do with an event or a certain period of time. It is also the study of what historians have to say about these issues, and how they agree or disagree in their arguments.
So, for example, there are many theories about the causes of the First World War. You can find a plethora of historians who have differing opinions about the true causes, from AJP Taylor to Fritz Fischer to Paul Kennedy.
In your notes and your essays you must always refer to the opinions of historians, and it is often useful to quote their writings. However, most examination boards want you to go further than this and critically evaluate their theories.
Critically evaluating historians
When you are making notes always put the name of the historian, the title of the book and the page numbers somewhere.
When you have finished reading, try to make lists of historians who agree on certain issues, and try to find examples of where historians disagree.