Hi! I just recently finished my Master thesis in history. It was completed with an oral exam, where one criticism was that some of my work had been addressed by others before. Now, I have always found it difficult to orient myself in the current historiography and I am now considering to take on a new research project. But I need to know what has been researched before. So my questions is: How do you best get a good (and preferably quick) overview of what has been written before and what projects might be new and fruitful? Encyclopedias, I suppose, are useful, but may be outdated or limited in information. Any tips on good and easy methods to get an orientation in the current historiography of a given field would be greatly appreciated. (I mainly focus on Sasanian Iran, but I am hoping for some general pointers and methods.) Thank you so much for your time!
Research encyclopedias and companions can indeed be a good place to start to get a broad overview of the topic--you'll probably know most of the fact, but look for recent entries in their bibliographies. Thinking of things here like Oxford Bibliographies Online (if your uni pays for access), Oxford Handbook to _____, the Cambridge Companion series, Brill's Companions, etc.
Unfortunately in your case, the Cambridge History of Iran series is from the 1980s so pretty much worthless in terms of current historiography. The New Cambridge History of Islam is much more recent, but I'm not sure how much "pre-Islam Persia" it covers.
Your next stop is the most recent publications in the field--again, not so much for what the individual piece says, but for its bibliography of other recent stuff. Look at recent issues of the major journals in your field; browse recent PhD dissertations (since PhD theses generally have a literature review--doing your work for you!).
As to coming up with a topic/original research, I like to bounce back and forth repeatedly between my primary and secondary sources. This way I get some guidance from existing scholarship on what are useful directions in the primary source so I'm not floundering, but I also can see where people have been so I know to take a different path. The key is to keep going back and forth rather than assuming one and done.