DialogBestPractices - Fluentui

Don't use more than three buttons.
Dialog boxes consist of a header, body, and footer.
Validate that people’s entries are acceptable before closing the dialog box. Show an inline validation error near the field they must correct.
Blocking dialogs should be used very sparingly, only when it is critical that people make a choice or provide information before they can proceed. Blocking dialogs are generally used for irreversible or potentially destructive tasks. They’re typically paired with an overlay without a light dismiss.

Keep the title as concise as possible.
Don’t use periods at the end of titles.
This mandatory content should explain the main information in a clear, concise, and specific statement or question. For example, “Delete this file?” instead of “Are you sure?”
The title shouldn’t be a description of the body content. For example, don’t use “Error” as a title. Instead, use an informative statement like “Your session ended.”
Use sentence-style capitalization—only capitalize the first word. For more info, see Capitalization in the Microsoft Writing Style Guide.

Don't restate the title in the body.
Use ending punctuation on sentences.
Use actionable language, with the most important information at the beginning.
Use the optional body content area for additional info or instructions, if needed. Only include information needed to help people make a decision.

Write button labels that are specific responses to the main information in the title. The title “Delete this file?” could have buttons labeled “Delete” and “Cancel”.
Be concise. Limit labels to one or two words. Usually a single verb is best. Include a noun if there is any room for interpretation about what the verb means. For example, “Delete” or “Delete file”.