On a blank piece of paper, create a sonicspace (a visual map) of the form of the piece (how sound evolves in the piece), and also any interesting sonic events that occur. Describe these events. Also note of when they occur in time (use the long edge of the page as the time line - i.e., from 0 to 5:12).
Also, describe the aesthetics of the piece, how it makes you feel (overall, and possibly at specific points in time).
Use any symbols you want to create your visual language (e.g., curves with or without color, geometric shapes, etc.) to create your map.
Obviously, you will have to listen to the piece a few times to begin understanding its structure better.