Some good nuggets and nibblets on story pacing in this two part article by Larry Brooks. I'm currently writing the next sequence of The Winchcombe, and one of the biggest challenges I face is with pacing.
Since I only publish a scene a week now (and it was still a problem when I was able to publish twice a week), I have serious problems with pacing. The last Episode, Opening Night, took place over one night in story time, but took months and months of real time to release.
Much of this is simply a problem with my chosen medium and method of publishing, but that means I don't have time to mess around with stuff that doesn't serve the story.
This is the key to effective pacing. Know what your scene is… why it needs to be there… and what it must do in terms of delivering specific exposition that thrusts the story forward.
All scenes are obliged to deliver characterization, so showing us something about your character is probably not the primary expository mission. The job of every scene is to take us deeper into the story… and to do with appropriate characterization.
Not to tread water, not to analyze, not to flashback or wax philosophic. This means you shouldn’t ever have a scene that exists solely to tell us something about a character, you need to show us something about her or him.
Which means, something needs to happen.
This is at the forefront of my mind with each scene that I'm writing.