To begin I looked into existing style guides to find out what would need to be included here are a few examples I have found.
‘A style guide is a set of standards for the writing and design of documents, either for general use or for a specific publication, organization, or field. (It is often called a stylesheet, though that term has other meanings.) A style guide establishes and enforces style to improve communication.’
From this I have created my own simple style guide for Stephen Fry.