Beginning at the Beginning
I have been making an unofficial list of the “world’s most commonly used writing axioms,” and I’m pretty sure in media res needs to be on there. In media res means “in the middle of things.” It is advice given to writers to start their stories with an action that will capture the reader’s attention. This action should be compelling—it cannot waste too many precious words on exposition, or “setting the scene.” This action should inspire curiosity, thus it should be chosen from the middle of the narrative (when approached in a chronological sense). Then we can spend the next part of the narrative backing up to figure out just exactly what this is all about.
Seems easy enough, right?
There is a problem, however, with the way in media res is being used by many writers today. In media res was originally used as a tool for selection; that is, it helped dramatists figure out which scene to begin their narrative with. So far, so good. Presenting a scene first indicates its importance to the whole, just as deciding which scene will come last indicates the dramatist’s moral intent through the fate of the characters.
A certain scene was chosen to initiate the action, to begin the entertainment.
But the dramatist did not go back and fill in the details of what happened previously—it was assumed that the audience would already have this information (which battle had been fought, who had been the victor, what situation these characters found themselves in, etc.).
By contrast, today’s writer frequently presents a scene from the middle of the narrative first, and then backs up to the beginning and tells the rest of the story in a strictly chronological order. The scene in question then recurs somewhere in the middle of the work. To begin in media res and then tell much of the story in a flashback is disconcerting—as readers, we will reject this timeline in favor of following the reading present. Basically, we forget about this lone, out-of-sequence scene, except for harboring a mild curiosity as to why it has been given such special placement and when it might recur.
I would argue for two ways out of this current dilemma.
First, if you are going to begin with a scene from the middle of the narrative, why not continue to utilize the narrative possibilities of flashbacks and multiple concurrent timelines to ensure that your first scene does not look like an ugly duckling?
The second and perhaps more cogent solution to the in media res dilemma is that once you have begun in the thick of the action, don’t backtrack. In media res means “in the middle of things,” not “in the middle.” If your first scene engenders interest, if it implies a world where there is something at stake and immediately transports the reader into a situation with dramatic tension, why not just continue from there?

Mariah Ashley said on Nov 3, 2011 at 12:00 PM:
aha! lightbulb! time to edit my story and start with the puking and end with the french canadiens!