One of the best enhancements Microsoft made with SharePoint from 2003 to 2007 is the inclusion of Content Management Server as part of the suite. Microsoft also renovated search as part of MOSS as well.
I had the pleasure of attending a search deep dive training session back in 07 and we went deep into relevancy and, as consultants, how to optimize the environment for search.
There were a number of things taken away from those sessions, but by far, the factors influencing search relevancy was a big one.
One thing I learned was, by far, one of the biggest factors influencing search relevancy is the page Title. Ideally, this field should have all of the keywords you would like the page to be searched upon.
From a design perspective, however, this could pose a problem if everything isn’t designed properly. At times I have seen pages titled "Home" or something like that. If this is a common practice within the enterprise, the SharePoint index would be chalked full of pages relevant to the keyword, "Home". This problem arises when the Title field is used within the page layout and may not contain relevant keywords.
Knowing this, what I would suggest as a best practice is to not use the Title field in the visual design of the page layout at all. I would keep it in the Edit Mode Panel (hidden) and create another title field to use for display purposes. That way, you can use the default field as a keyword tagging container.