Structuring your Documents for Maximum Reuse, Janice (Ginny) Redish, Best Practices, June 2000.

Ginny Redish outlines a step-by-step procedure for creating structured documents.  Even if you aren't yet considering single sourcing, you'll find that structuring documents is an extremely useful, time-saving technique. It works in traditional publishing and is useful for individual writers in any situation where they have to create the same type of document many times. It is essential for teams of writers who are contributing parts to a large document or to a set of documents.  (link coming soon)