There’s some good information out there about how to set this up, but I
wanted to clarify a few points in the hope of saving others some time.

The basic steps are:

1. Obtain the Fully Qualified Domain Name (FQDN) for your MOSS site.

2. Create your Google Analytics account (see detail below). FYI, You don’t need
   to pass any authentication in order to track hits to your site.

3. Add the GA tracking code to your site’s master page within the HTML tags,
   which will allow you to analyze all the sub-pages, not just the home
   page.

Sadalit Van Buren presents a nice overview and addresses a couple gotchas. Comments are also very useful.