Begin by identifying logical keywords  -- key concepts -- for your search. Start Low Tech: Get out a piece of paper........

Ask yourself:

• Who? 
• What?
• When?
• Where?
• How?
• Why?

Other good questions to stimulate thought:

• What specific word, phrases and/or names will occur in the documents I want?
• Are there any unique names or terms of art?
• Are there equivalent or interchangeable terms?
• How might the author think?

If you are searching a Directory or a Gateway, ask "What’s my broadest subject?" as that is your starting point for a search through their topical indices