I've created a cheat sheet for Joomla 1.5 templates. Soon to be available on a nice printable page.

Include a Module:

<jdoc:include type="modules" name="theName" />

Display the main content or component

<jdoc:include type="component" />

Display Breadcrumbs

<jdoc:include type="module" name="breadcrumbs" />
//Use the following for 1.6
<jdoc:include type="modules" name="breadcrumb" />

Live site Name

<?php echo $mainframe->getCfg('sitename');?>

Administrators Email

<?php echo $mainframe->getCfg('mailfrom');?>

Current template directory is

<?php echo $this->template?> directory

The live site URL

<?php echo $mainframe->getCfg('live_site');?>

This is how I created a path to my tpl directory, it had to be in the header.

$tpl_path = JURI::base() . "templates/" . $this->template . "/";

The above are good tricks, also checkout Joomla Docs.