In honour of the ongoing Rugby World Cup, I am going to get metaphorical.

Imagine history as a game of rugby. Usually, a historian's role is as a player in the game - we are each seeking to grab the ball of history, and push our interpretations forward towards the tryline of truth (and hopefully land the conversion of consensus), against the opposition of other historians who dare to disagree with us. There is possibly some argument to be made about the forwards representing empiricists, doing the hard, gritty work that the flashy theory-driven back line can exploit and get the credit for, but that's getting subjective. There's another argument to be made about European teams playing a staid, boring game which doesn't move a lot and involves too much kicking, while the innovation and elan comes from elsewhere in the world. The point is, we are getting our hands dirty, seeking to advance and substantiate our own views and to change the game itself.

When we do historiography, our role in the game changes. Now, we are the referee - it's our job to understand the state of play as a whole, to understand the position of each side, how they are interacting and to take note of what they are trying to achieve at this point in the match. Importantly though, this doesn't make us uninvolved or entirely detached - you are seeking to judge and shape the game indirectly, by evaluating the actions of players and judging their efforts. Alongside taking note of how the game has evolved up to this point, the lines of debate and disagreement, the outstanding questions that historians players are seeking to answer and the methods and sources they are using, it's your job to try and evaluate the field itself, identify neglected questions, suggest sources and approaches that might form the basis of the next phase of the game. As such, there is still a significant element of analysis and argument - you aren't just describing or summarising what others have done. Much like the referees in this World Cup, it's your job to do as much as possible to shape the result of the match.

Been there!

I very much remember the first time I had to write a historiographical essay and being incredibly intimidated for pretty much the reasons you mentioned ("Is this supposed to have some sort of thesis? Am I making an argument?").

A historiographical essay is, in large part, an enhanced literature review (if you find that less intimidating of a term; if not, forget I said that).

All of this depends heavily on your particular field of history, but you're on the right track. Things to consider include:

1. Where did the subfield originate? How did it first present itself as a distinct field of study, and what was the impetus for it?
2. Who were the first scholars to articulate theories? Who picked up their trains of thought and where did they take it?
3. Were there opposing views? Who were they articulated by? What was the basis of their arguments?

And then you'll follow this down to the current generation of scholars. You may find it helpful to group scholars together into schools of thought if this isn't something that's been done already.

Finally, depending on your the parameters of the assignment, you can situate yourself in the argument at the end, either in terms of where your own research is going to fit, or where you still see that work needs to be done or there are questions that need to be answered. (This is very useful, for example, in preparing a historiographical essay that's going to be part of your thesis prospectus or portfolio; if it's for a class/module it might be less important to do, but still a good note to finish with).

Check out the publication History Compass -- there are a number of historiographical essays on various topics in there, and they're all fairly short!

Context: grad historian. I always hate writing historiography papers but they are necessary, especially for dissertations and theses. Basically what I do is find trends among different historians. If historian A and B use similar evidence or focus on similar themes, but Historian C, D and E dont, that's significant. Then find out what C D and E are doing. Personally I like to write mine with a stronger chronological focus. It allows me to focus on the context in which the pieces were written rather than grouping them in themes as themes can downplay context (being that themes can stretch over long periods of time). Really what you're doing is commenting on how these historians discuss history. Does their approach have a bias? Is there an inherent flaw? What conclusions are brought up when compared to this other approach. One area that always helped me to write them is the intro section of a book. Usually they will write about why they chose their method or the historiography of that specific topic. Hopefully that helped at least a little. May I ask what the topic is?

To wrap my head around historiography, I typically look up a few recent books, read their introductions and any reviews, and perhaps some recent articles by the same authors. Then I start working my way backwards: Well, if author X says his work responds to Y, what did Y think her work was doing? And if Y was responding to Z, what about Z? Not all authors are great at representing their own work, much less the work of others, and I find that this approach helps me see how key questions or critical evidence have changed over time.

Working with individual sources can be more tricky, since you're actually investigating the reception history of the source among modern historians. Discussion tends to be less specific about evidence and approaches, but the underlying problems are the same. Historians, over time, focus on different parts of a text, and they ask different questions about it. I think the trick is to see this as its own story of change over time, which lends itself to a basic narrative, rather than a vague commitment to historiographic themes, which suggests a topical structure that I find difficult to implement.