The things below are not in any particular order of “naughtiness” but all are techniques/activities that should be avoided at all costs as they can get you banned from Googles index!!
Link Exchanges and Bad Neighborhoods
Linking ordinarily would make you a good neighbor and a good citizen of the internet. However, just because someone links to you does not obligate you to link back to them. Sometimes you do get judged on the quality of the friends you keep. Google calls spamming sites bad neighborhoods, and linking to them and links from them can have a negative impact on your search engine placement/ranking.
Link exchanging programs, paid link placement, and other scammy schemes are also things that Google frowns upon. You may get away with it for a while, but eventually, Google will catch onto the scheme, and your search results will drop spectacularly. Many disreputable SEO companies employ the tactic of creating an artificial web of links on unrelated websites. Which at first can make it look the website is going up in the search engine results but Google realised pretty quickly and will punish the website by dropping it down in their results or even go as far as to ban the website from the search engine results.
Create content automatically
You should take the time to create original content. Do not use software to create your web pages automatically.
Automatically created content Google hate so much that it is targeted by Google’s Panda algorithm, so this is a good way to get banned on Google.
Use keyword rich doorway pages and cloaking
This is an old method that Google still hates, especially if you combine it with automated content. If you create pages that contain a lot of your keywords just for search engines. Then redirect the real visitors of your website to other pages on your site (cloaking) then Google will hate you and more than likely ban you.
Top tip: Redirect your users to pages that are totally unrelated to the content of the doorway pages. Chances are that Google will ban your website even quicker then.
Hide text on your web pages
A standard old technique that Google still hates!! If you enter keyword rich text on your regular pages and then hide it so that your website visitors cannot see it Google will know and will penalise you and even maybe ban you for it. People hide text on a page by using white-text on a white background, with CSS, or with a very small font size.
The more text you hide on your pages, the more likely it is that Google things that these web pages are spam and treat you like spam.
Get links in bulk
If you automatically submit your website to thousands of forums, or automatically create forum profile links, or buy as many links as you can on as many websites as you can you then Google will hate you and penalise you . and even more so if these links always contain the same anchor text.
You need to get proper links not spammy one and Google quality back links will improve your rankings on Google.
Distribute Viruses, Trojans, or Other Malware
If your site is distributing a virus, trojan, or other malware, Google’s going to remove you from their index for the public good. Well durrr!!!
If you’ve been hacked and have cleaned up your site, you can contact Google to let them know you’ve rectified the problem via a Google Web masters tool account.