Good Online Indexing: It Doesn't Happen Automatically 
Indexing online information is a key skill for online information developers, yet not much information exists on how to do it right. After defining online indexing and briefly presenting the research the authors were involved in, the article provides all the key ingredients for creating a good, searchbased online index.
Berry, Robert R., Ralph Earle and Michelle Corbin Nichols. STC Proceedings (1994). Articles>Indexing>Online