Here is a good resource to teach yourself sentence diagraming or to use
in the classroom.  It is a book of practice exercises. I have had
great response from students in a traditional grammar course, especially
those who have never diagrammed.
  Dressel, Mark, and Greg Carnevale.  "Better Sentence Structure
    Through...Diagraming." Book 2. Grand Rapids, MI:  Instructional Fair,
    n.d.  ISBN:  1-56822-176-2
I bought it at a teacher supply store.  It gives the classroom teacher
permission to photocopy the exercises for class distribution.

Book 1 begins with simple sentences.  Book 2 ends with compound-complex
sentences.--Lori Pahde