Wikipedia's Manual of Style

The Manual of Style (often abbreviated MoS or MOS) is a style guide for all Wikipedia articles. This page and its subpages cover certain style topics (such as punctuation) in full, and presents the key points of others. The subpages also provide detailed guidance on particular topics or subject areas.

I often wondered how the pages on Wikipedia are so precisely and well written. While browsing, I came across Wikipedia's page on "words to watch" and from there I landed on its Manual of Style.

It is an excellent guide providing lots of examples and reasons as to why a particular style should be used. MoS provides guidelines for tiny-little-things including how dates or times should be formatted, and when to use periods in abbreviations and when not.

Link: http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style