<form action="http://www.google.com/search">
  <input name="q" size="70">
  <input type="hidden" name="as_oq" value="test review evaluation">
  <input type="hidden" name="as_eq" value="buy.now special.offer free.download">
  <input type="submit" value="Search">
</form>

http://searchlores.org/termisearch.htm

The Google search URL accepts two fields, `as_oq` and `as_eq`, which give additional required or forbidden keywords for the search.  This allows to create search forms which add preset keywords.  In the search form below, one of the keywords test, review or evalutation is required, and none of "buy now", "special offer" and "free download" may be present.

Google search form with additional keywords

search, google

HTML