I found it necessary to change one line to make it clear to users that apostrophes should be omitted when searching for keywords (e.g. "St Pauls Church" not "St Paul's Church").
In \lang\english.php
Change
Quote$lang_common['keywords'] = 'Keywords'; // cpg1.5
to
Quote$lang_common['keywords'] = 'Keywords (omit apostrophes)'; // cpg1.5