1. Search Tripod for either keywords that seem relevant to your topic, or for a specific book that seems relevant.
2. Go into Tripod's Books and More search results. View the full Tripod page for a book. (example Tripod page for a book)
3. Look at the Subjects listed for the book. (in the example linked above, the book's subjects include "Cezanne,Paul > 1839-1906 > Criticism and interpretation)
4. Look at the Tripod pages for a few other books. Write down subjects that seem relevant - these can become useful search terms.
5. Try running a Tripod Advanced Search that looks for books matching various combinations of these new search terms.