A common need in SharePoint 2007 is to create your own Content Types (great new feature) with a bunch of custom columns for metadata tags. The process for this is documented all over the place and easily found, so I won't go into it here. But, what I do want to cover here is how to get those properties setup as "Managed Properties" so you can search only on a given set of your custom columns on the search pages.
To do this is basically straight forward and, again, is documented in a lot of places on the web. The basic process is to nav to the SharedServices Admin site and click Search Settings. Then select the link for "Managed Properties". Now click the button labeled "New Managed Property". On that next form, just fill out the appropriate information and click the Add Mapping button. Enter your custom column name and select it from the list, click OK a couple of times and done!
Problem:
Well, what you might notice, if you are so lucky as me, is that you CANNOT add the mapping to your custom column. Why Not? It just won't show up in that danged list!!!! Hmm, try forcing a full crawl, still no luck. Delete all my indexes (don't recommend this on production too often) and force a new crawl, STILL no luck.
Solution:
As this is all happening on a pre-production system, we didn't have too many docs out there using my new content type. Additionally, most (if not all) of our custom columns are optional, meaning that the docs might not have values for those fields yet. And there's the rub! Until SharePoint crawls at least one document with a value for a custom column, that column cannot be mapped to a Managed Property. So, I uploaded a junk file and set ALL of my custom columns to contain junk data. Forced another crawl, and I HAVE MY MAPPINGS. Now I can setup my custom searches to pull the way I want.
Happy Indexing and Searching!