OCLC’s WorldCat search capabilities have expanded enormously since PRISM days. If you want to spend a long time exploring everything available to you in WorldCat searching, take a look at Searching WorldCat Indexes: “comprehensive information about indexes used to retrieve records from WorldCat.” This will let you go quite deep into such matters as indexing and search enhancements.

For more accessible and quicker reference, this document links to several interface-specific guides, including Connexion: Searching WorldCat Quick Reference, applicable to both the browser and the client; Cataloging: Search WorldCat for the client, and Find Bibliographic Records for the browser. There are also links to configuration guides for OCLC Z39.50 access to cataloging and to FirstSearch.