The IEEE Guide to Writing in the Engineering and Technical FieldsKmiec, D., Longo, B., & Longo, B. (2017). The IEEE guide to writing in the engineering and technical fields. ProQuest Ebook Central.
Read chapter 3, “Writing to Know: Informative Documents.” Read this entire chapter carefully; you will find value throughout. Pay specific attention to pages 104-108 where specifications are discussed.
The IEEE Guide to Writing in the Engineering and Technical Fields is an authority reference to elements of process, style, audience, format, and tone associated with writing technical documents. As a technical manager or technologist, this will likely be an important document for you to reference as your career develops.