Christopher Nolan drew out a map of the film's five dream levels and how they intersect across the linear narrative. Not only is it a clear explanation of what's happening on every level at every moment, but you can see in Nolan's notes his concern about the plot and the different length of time on each level and how it might affect the parallel plots.
Nolan carefully tracks Fischer's place throughout the levels, and even changes the dreamer on two levels. Press the image to see a larger version.
Uploaded by Incontention.com