Here are some signs that a piece on the popular Christmas carol is worth your (and your listeners') attention:
1. Melodies are not monotonous and have intentional direction.
2. Rhythms are unified but also augment each other in various parts.
3. Harmonies are stylistically appropriate and colorful.
4. Dynamics display the tune and other parts in a most comprehensible fashion.
5. Registration cleverly uses resources of the instrument and convey the meaning of the text.
6.Texture helps displaying the possibilities of the theme.
7. Form is clear yet not utterly predictable.
Keep in mind the above signs as you prepare for the upcoming Christmas season and you will not fall into a common trap of playing crowd-pleasing but artistically dull music which in turn will help your efforts to become a trusted go-to resource for high quality organ music in your community.
By the way, as I was preparing for my upcoming recital of organ improvisations on the Story of the Nativity of Jesus Christ on December 20 at Vilnius University St. John's church, a few days ago I wrote a piece "The Annunciation" for the organ on original themes. Here is the score, if you want to check it out.