The project style guide helps your team to write clear and consistent content across all channels and it serves as an important reference for the project team. If your project is a corporate brochure then there is probably no need to create an elaborated style guide. But if it's a website or a marketing campaign with several authors and stakeholders then a style guide is a necessary foundation.
The style guide is divided into three parts: Voice and Tone, Grammar and mechanics, and Structure.
Voice and Tone
This section treats the more emotional side of your content. Describe the general style the content should be written in, like the use of humor ( "straight-faced, subtle, smart but not snobbish") or wording ( "demystify B2B-speak and educate instead"). Or something like "Use a formal and active voice. Avoid passive voice".
Grammar and mechanics
Here you could give some guidelines concerning abbreviations and acronyms, capitalization, punctuation and text formatting.
Sometimes articles should adhere to a certain structure like for example "Headline, subline, introduction (max 100 words), main body, conclusion, references, author and date". This is the place to describe what you are expecting from your authors.
Your style guide will be most successful when you illustrate the rules with practical examples. Like: "In active voice, the subject of the sentence does the action. In passive voice, the subject of the sentence has the action done to it. Yes: Marti logged into the account. No: The account was logged into by Marti."
The Styleguide is accessible for every team member of the projekt.
But only the administrator and projektmanager are able to edit it.