From SFWiki

A wiki (such as SFWiki) is an editable knowledge base; SFWiki consits of user-created pages or articles about the San Francisco Bay area. It contains all kinds of useful information about life around the bay, and this information is contributed and edited by readers of the wiki. One of the great things about a wiki is that if you find an error, you can easily correct it! Simply click the edit tab at the top of the page, and you go to a web page form that lets you change the content.

Syntax

Of course, you might want to format the text that you've edited. For some help with the syntax used by SFWiki, check out Help:Editing.

Where to Start Editing

If you want to contribute, but aren't really sure where to start, check out the Requests page. This is page where people have requested that certain pages be created. Additionally, you could look at Special:Wantedpages. This is an automatically generated page that contains a list of the non-existent pages that have the most links to them.