Basic searching
+elephant
title:elephant
title:"grey elephants"
ele*
ele*ant
Additional filters
category:abc
category:abc,def
since:yyyy-mm-dd
till:yyyy-mm-dd
user:author-name
Searching on tags
tags:big,noisy
Global searching
search:all
site:elephants
site:elephants,lions
KiCadHowTo does not have an associated forum, but I could not see how to edit off the forum related radio buttons!
Neither have I, as of November 2011 at least, "tagged" the site's pages.
(You are just as well served by the search box in the page header, apart from the advice to the right of this on wildcards, etc.)