Google has launched an improved version of its URL removal tool in Webmaster Tools, aimed at making it easier to request updates based on changes to other people's sites.
Google suggests that you could use the tool if a page has been removed completely or if it has changed, and you need the snippet and cached page removed.
"If the page itself was removed completely, you can request that it's removed from Google's search results," says Google Webmaster Trends analyst John Mueller. "For this, it's important that the page returns the proper HTTP result code (403, 404, or 410), has a noindex robots meta tag, or is blocked by the robots.txt (blocking via robots.txt may not prevent indexing of the URL permanently). You can check the HTTP result code with a HTTP header checker. While we attempt to recognize 'soft-404' errors, having the website use a clear response code is always preferred."
For submitting a page for removal, just enter the URL and confirm the request.
"If the page wasn't removed, you can also use this tool to let us know that a text on a page (such as a name) has been removed or changed," says Mueller. "It'll remove the snippet & cached page in Google's search results until our systems have been able to reprocess the page completely (it won't affect title or ranking). In addition to the page's URL, you'll need at least one word that used to be on the page but is now removed."
Webmasters are instructed to enter the URL, confirm that the page has been updated or removed and that the cache and snippet are outdated, and enter a word that no longer appears on the live page, but still appears in the cache or snippet.