Today, I was working with a client and describing how to modify the content query web part and display additional bits of information from a content type.
"First, you configure the CQWP to connect to its data sources, then you export it to your workstation, modify <CommonViewFields>, upload, remove the original and now it’s ‘primed’ to display those other columns. Next, open up SharePoint designer, navigate to the site collection root and locate ItemStyle.xsl. Copy one of the templates as a useful starting point. Go back and modify the CQWP to make use of this new template. Finally, modify the template to render your new fields! (Don’t forget to check it back in so that other users can see the results)."
It’s all quite clear to me (and most of us SharePoint developer types) what’s going on and how it’s quite nice, really, that the data retrieval aspects of the CQWP are so well-separate from the data presentation aspects. But, it’s not so easy to explain, is it?