It discusses how to prepare copy, acceptable abbreviations, punctuation, style and more. Make your meaning clear in as few words as possible. Simple, direct sentences in short paragraphs. Just make sure you're presenting a series of facts in as direct a manner as possible. No redundant or superfluous words, sentences or paragraphs.
Repetition is the grossest form of wordiness.
It results from poor organization. This especially comes up when you use quotes from multiple sources that give the same information. Limit each sentence to one idea or a range of closely related ideas. Otherwise, sentences can take off in several directions at once. While you need to write in everyday language, avoid colloquial expressions, abstractions and jargon.