Search Access - Best Practices

I've been searching thru the documentation archive on some sort of article on best practices for search functions on a Drupal site. One module I did put in not long ago that was a tremendous help was Search Configuration:
http://drupal.org/project/search_config

This really helped in setting up permissions based upon roles.

However, that doesn't seem to be what I'm looking for in so far as allowing general visitors access to the search function. Back before this all started, the sites involved where being hammered by so many search engine requests they were making the site non-functional. Since shutting down all public access to the search box that has certainly stopped that; however that isn't very desirable either! Is there some way to limit the search function to just published content in the sitemap or something of that nature?

Thanks for all suggestions!