Here's a list of resources, for those who are new to wikis, to figure out how to add content, format, make changes, etc.

WikiStyle is a basic formatting guide covering:

Text formatting

Lists

Character Formatting

Sections

Other

Links

Pictures

Uploaded Files

Tables

Table of Contents

Use WikiStyle Characters Normally

More

Special Pages

Advanced Wiki Style covers advanced formatting:

Table of Contents

Text size

Fonts

Color

Links

Escaping code (or using wiki special characters as normal characters)

Indenting paragraphs

Blank space between sections

Enhanced SideBar

PB Wiki Tips has recommendations about improving the look and feel of your wiki, and a bunch of HTML info:

Make your wiki easier to read

Make your wiki easier to edit

Add a guestbook

Looks

Using HTML

Usability Tips

Cool lesser-known tags

Unofficial wiki FAQ currently more useful than the Official FAQ, for some reason.

For advanced geeking:

PB Wiki Forum is a forum for wiki users, that includes a very useful tips discussion area.