I recently saw 20 position change in search engine rankings on
Golf in Ireland Mount Juliet Golf Course Ireland Parkland Golf Course Ireland when content was changed, just by adding 3 extra keywords into the footer of the site.
Content in Context is probably the most important factor. I usually try keep the theme or context of page content to about 2 or 3 key phrases. I think this works well.
PS - Apologies for the long link ( I tried simply adding a web address to the post !)