For opening study, while I have occasionally run across some excellent resources, it has been difficult to find published works which take a holistic approach to explaining opening play, which should include the typical middlegame plans that result from an opening. Too often opening lines are presented and analyzed up to the middlegame, then abruptly abandoned for the next line. This means that someone who is an openings specialist, especially at the Class level, can easily fall into the trap of knowing what to do in the opening phase, achieving a good position and then quickly botching it a few moves into the middlegame.
I'd therefore like to start highlighting resources that are models for a comprehensive approach to opening study. Some are already mentioned on this blog as review summaries of books or DVDs that I've completed. The one I'm highlighting today is the Chess.com article by WIM Iryna Zenuk Typical Positions (Part 2). It is humble, practical and shows how an improving player can research and better comprehend key lines in their chosen opening. In this case, she looks at some key Queen's Gambit Declined (QGD) positions and the typical plans for both White and Black, using her own recent Philadelphia Open game as the starting point and then examining how top-level professionals have treated the positions. Even if you don't play the QGD, a look at the methodology and ideas can be valuable. I noticed some common themes with some English Opening positions, for example, that involve a space advantage for White and an open a-file.
This may seem like a lot of work - and it is. That is one reason I want to point out these atypically useful opening resources which offer us specific revelations of middlegame plans. It still requires some effort to understand and digest the analysis, but the insights provided by these model opening studies can save a player a great deal of frustration (and losses).