You can use wiki plugins to:
Many plugins are enabled by default. The others can be enabled easily from the Text Area Admin page. As a security measure, some plugins require admin-level approval before becoming "live" on a page.
icon and then click on 'Plugins help' for a list of plugins and their descriptions with buttons for inserting the syntax and linking to the documentation.
The way plugin syntax works in general is described below. The individual documentation page for a plugin also gives examples of the specific syntax for that plugin.
There are two basic styles of syntax, upper case, which works for virtually all plugins, and lower case, which works for plugins that do not require a body.
This syntax works for virtually all plugins (an exception is {maketoc}) and here is an example:
{PLUGINNAME(parameter1="value1|value2" parameter2="value")} content affected by plugin and called body or data {PLUGINNAME}
For plugins that do not require a body (i.e., content between the beginning and ending plugin tags), the lower case syntax can be used (since Tiki6). Here's an example:
{pluginname parameter1="value1|value2" parameter2="value"}
Here's what's different about the syntax for these:
If not enabled by default, the site administrator must enable a plugin before it can be used by (since 3.0) going to Admin Home > Editing and Plugins > Plugins (tab) and checking the "Enable" box of that plugin and clicking "Change Preferences."
On the same tab (Admin Home > Editing and Plugins > Plugins (tab)), a feature called "Enable edit plugin icons" can be enabled, which will place an 
icon wherever there's a plugin. This edit icon will display a popup input form when clicked so that the plugin can be edited without editing and saving the whole page.
Also, "Toggle display of section and plugin edit icons" can be enabled (at Admin Home > Wiki > General Preferences (tab) > Edit (section)). This will place an icon at the top of every page for turning section and plugin edit icons on or off with a single click (
to toggle on and 
to toggle off).
Plugins that are a potential security risk require approval by an administrator before they can be used - a notice will appear when that's the case.
There is a setting called "Plugin pending notification" in "Admin home > Editing and plugins > Plugins (tab)", which allows users in groups with the permission tiki_p_plugin_approve to receive an email notification each time a new plugin call is added in a wiki page as pending approval.