Add Custom Column Data to the Content Query Webpart XSL

The Problem: You have just added a new column to a content type. Authors are adding data to this field but its not showing in your content query webpart. 

Solution: Edit the webpart and XSL to add it. Here is how to do it through Sharepoint Designer

1. Open the Site Settings > Site Columns view to get the Name of your Site Column, It's not the "title" and it is NOT shown in the UI anywhere. You have to get it from the url.
   Note when you hover over a column, or click it, you will see the word "field=theNameofYourColumn" in the URL. Find this and copy it. In the example below I am hovering over Carousel Hero and the field name at the bottom is "TeaserRichText" this is the word you will need.
   
2. The other thing you will need is the type: In the example above it is "Publishing HTML" - but again, that is the title, you need the actual short name (in this case "HTML") here is a list of how they map:

   Type	Display
   TaxonomyFieldTypeMulti	Managed Metadata
   RatingCount	Number of Ratings
   Text	Single line of text
   Boolean	Yes/No
   Guid	Guid
   Choice	Choice
   Image	Publishing Image
   User	Person or Group
   Currency	Currency
   URL	Hyperlink or Picture
   Note	Multiple lines of text
   SummaryLinks	Summary Links
   Counter	Counter
   Integer	Integer
   Number	Number
   Lookup	Lookup
   Computed	Computed
   Integer	Integer
   DateTime	Date and Time
   Choice	Choice
   Number	Number
   TaxonomyFieldType	Managed Metadata
   Recurrence	Recurrence
   HTML	Publishing HTML
   File	File
   UserMulti	Person or Group
   AverageRating	Rating (0-5)
   Computed	Computed
   ModStat	Moderation Status
   AllDayEvent	All Day Event
   AllDayEvent	All Day Event 11
   CrossProjectLink	Cross Project Link

   Source: http://social.technet.microsoft.com/Forums/ar/sharepoint2010programming/thread/8fc8e9df-4e89-42c9-a858-e15c59ca616e
   3. Edit the webpart - Note that the way Sharepoint works, the webpart you see on the page is a copy of the one in the catalog. It is copied WHEN YOU ADD IT TO THE PAGE. If you change it catalog, it will be updated for any NEW webparts added based on this, but existing ones will either need to be added to the page again, or edited individually.
   In Sharepoint Designer open All Files > _catalogs > wp >  yourwebpart.webpart (ours is xwidget.webpart - a modified version of Content Query webpart)
   Find this line in the:
   

   This is where you add the "Column Name, Type;" - adding it here will pass it to the XSL4. Edit the XSL - Your webpart also has a line that calls the correct XSL. it looks like this:
   

   Open that file in Sharepoint Designer. The values from above can transformed, manipulated, or just rendered with the following:

   Notice the @ sign. Others values that are passed as parameters or variables and have a $5. Replace the old webpart with the new ones - remember these are copies on the page, not tied to the original in the catalog.