Updated Specific Quality Webmaster Guidelines

Updated Webmaster Guidelines with more about the irrelevant keywords, rich snippets, monitoring site for hacking, removing hacked content, removing user generated spam.
Specific quality guidelines outline following techniques to avoid [ the updated and previous ].

updated 10/02/2012	updated 09/18/2012
Automatically generated content	Avoid hidden text or hidden links
Participating in link schemes	Don't use cloaking or sneaky redirects
Cloaking	Don't send automated queries to Google
Sneaky redirects	Don't load pages with irrelevant keywords
Hidden text or links	Don't create multiple pages, subdomains, or domains with substantially duplicate content
Doorway pages	Don't create pages with malicious behavior, such as phishing or installing viruses, trojans, or other badware
Scraped content	Avoid "doorway" pages created just for search engines, or other "cookie cutter" approaches such as affiliate programs with little or no original content
Participating in affiliate programs without adding sufficient value	If your site participates in an affiliate program, make sure that your site adds value. Provide unique and relevant content that gives users a reason to visit your site first
Loading pages with irrelevant keywords
Creating pages with malicious behavior, such as phishing or installing viruses, trojans, or other badware
Abusing rich snippets markup
Sending automated queries to Google
Engage in good practices like the following: Monitoring your site for hacking and removing hacked content as soon as it appears Preventing and removing user-generated spam on your site

from
http://support.google.com/webmasters/bin/answer.py?hl=en&answer=35769