Obviously it's recommended that a reader has seen the entire series (or at least one or two seasons past the season being studied), since events presented as a "mystery" in a particular episode are laid bare here as factual events (spoiled). A good example is the question of who poisoned King Joffrey: in the episode in which that occurs, below I simply name which characters were responsible.
Personally, I have only seen the entire series once, with some favorite arcs revisited. The below chart was pieced together from the detailed synopses found on Wikipedia, and will probably need revision to different degrees. Nonetheless, it may help explain how certain things came to happen, which at the time seemed (at least for me) "out of the blue" (for example, Red Wedding, Knights of the Vale at the Battle of the Bastards, etc).
Reading the Chart:
The main goal of these analyses was to situate historical events (well, fictional, I have to keep reminding myself) in time, by place and by character. To facilitate the 4-dimensional aspect of this matrix I first placed time (episode) in descending rows and location in columns (north to south listed left to right, generally). Then, characters were color-coded (see guide below), with character colors blended when two major characters were equally featured in the same event. Finally, the events themselves were captioned in the boxes as succinctly as possible. In each chart there is also a "banner" box summarizing the main events which occur in that season.
UPDATE: I decided to put these up at full size on a different blog with a wider playground so please click below!