Thinking about what your audience wants to know will provide a guide to what needs to be included and in what order. Material that is not directly related to the key messages can be moved to an appendix, or a link if you are writing online content.

For example, some reports (especially government or scientific reports) can get bogged down with details of what was done, rather than what was discovered, because the author is too close to the subject. Unless the process itself is a key part of the message, it can be moved to an appendix and summarised in 1 or 2 paragraphs in the body of the report.