Adding tp=1 to your site url like this:
yourdomain.com/index.php?tp=1
will show the Template positions for quick reference.
In Joomla 1.6 this is not enabled by default as it was in Joomla 1.5.
To enable this in Joomla 1.6 go to Extensions -> Template Manager, and click the Options button in toolbar top right.
Set Preview Module Positions to Enabled.
