One useful technique I have started using recently is a spreadsheet which briefly lists each scene. I then track where all the main characters are while the scene is being enacted. This prevents characters suddenly appearing in impossible places or while they are meant to be some place else.
The spread looks like this for my current work in progress:
I also use the spreadsheet to track other elements of the longer story from scene to scene:
Character change from scene-to-scene/chapter-to-chapter
Plot development
Developments of theme(s)
Character relationships (romantic and otherwise)
Symbolism
Character mood/emotions
The progression of sub-plots (which are often not played out over consecutive scenes)
Character changes during sub plots
One of the main aims for me, is to ensure every type of progression happens logically and incrementally.
By entering ever scene in the spreadsheet, I can check each scene flowas from the one before it and contains a trigger for the next scene in the seuence.
It also enables me to work in litte character vinivrettes - very small character developments - that last only a couple of scenes. My readers may not notice these, but they add depth to the supporting characters.
Hope you find that of use.
Nick
