I have tried too many method to change Google Search URL

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Febwed FebWed: I am the beginner in SEO. I have tried too many method to change Google Search URL, but still cannot show our sub directory in of website domain in Google search result. (Now showing www.example.com, but I want to show www.example.com/categories) I have tried to add the href="http://www.example.com/categories"
  rel="canonical"> and <meta name="og:url" content="http://www.example.com/categories"> , but it still show the www.example.com in Google Sesrch result. Did I do something wrong? or could any Professional can tell me what I should follow to do? Thanks!
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  Edwin Jonk: I would go the Google Webmaster Tools and fetch as Google [1] under "Crawl". If you click on the status it will bring to the tab "Fetching". This is the output send by the server to Googlebot. In that downloaded HTTP request I would look for "noindex". The noindex can be served as a http header or as a metatag [2].
  
  [1] ;https://support.google.com/webmasters/answer/6066467?hl=en
  [2] ;https://developers.google.com/webmasters/control-crawl-index/docs/robots_meta_tag?csw=1