Writing in an encyclopedic style and a formal tone is important when adding new content to Wikipedia. Instead of essay-like, argumentative, or opinionated writing, Wikipedia articles should have a straightforward, just-the-facts style. Here are examples of the do’s and don’ts of encyclopedic writing.

Do:

1. Use plain language
2. Be brief 
3. Cite sources to back up factual claims
4. Attribute viewpoints to the people who hold them
5. Avoid stating conclusions, except when attributed to a specific source 
6. If editing an existing article, be consistent with it's existing style and language.
7. Layout matters. Good articles start with introductions, continue with a clear structure, and end with standard appendices such as references and related articles.
8. Paragraphs should be short enough to be readable, but long enough to develop an idea. Overly long paragraphs should be split up, as long as the cousin paragraphs keep the idea in focus.
9. The tone should always remain formal, impersonal, and dispassionate.
10. Avoid using jargon whenever possible. Assume readers are reading the article to learn. It is possible that the reader knows nothing about the subject.

Don't:

1. Don’t create new essay-like articles or sections.
2. Don’t structure your writing as an argument.
3. Don’t use “weasel words” (like “most experts agree” or “some people say”).
4. Don’t use colloquial language or slang.
5. Don’t use “peacock terms” (like “great”, “extraordinary”, or “intrepid”).
6. Don’t inject personal opinion into the writing.
7. Don’t use overly complex language and sentence structure.