When working up some process documentation, our group had a little bit of a revelation:
Documents exist to make a decision.
This single statement really helped us streamline what we were doing with our documentation, and our process itself. At each stage, we asked "What decision is trying to be made? What information is needed for that decision?" Everything else was junk, and we cut it out of the document.
Every time I write a document now, I ask myself that question.