In the course of a day as a Drupal Themer, I need to code a wide variety of functionality into a given site I'm working on. I try to follow Drupal best practices as well and this usually means implementing theme preprocess functions; these become key to a Themer's toolbox.
In my last article I demonstrated how to extract basic data from field array elements which is ideal for custom node theming. The key to this is using *field_get_items*. I'll expand upon that by adding in additional Drupal API functions to enhance and format these Field array elements.
In this article, I'll show how to really dig into data associated with a field and for that I'll use a preprocess function in your theme's template.php for the logic and then a variable for presentation in a custom node template.