As websites grows, searches like "LIKE title '%search term%'" becomes unreliable. There are very good solutions like Sphinx, Lucene, etc, but not surprisingly, you can't always have Sphinx installed (shared servers again) and other solutions should be chosen. [...] How you start indexing data? Zend manual has very good examples how to start with Lucene.
He includes some basic code to create an index for your data (his example pulls information from a database) and how to search that data for a string ('title:"Apple MacBook"' in his case, searching specifically on the title field in his index).