One of my major stumbles was dealing with ControlTemplate and ContentControl which can save a lot of time when using the same information or control designs throughout a project.
The ControlTemplate sets a framework for a specified section of the UserControl. These can be specified as part of a style or, separately in the ResourceDictionary. Either way, the template is linked to the UserControl with a x:Key (or the Style's x:Key when in the style. The style sets the overall look and feel of a specified section of an UserControl).