I pulled some of this from Inbound Marketing, which I recently reviewed.
Google is notorious for constantly changing its formula as to what it deems SEO worthy. One month you might be riding at the top of search engine results, and the next, not in the top 3 pages. While I don’t pretend to know how they operate their complex spiders, I do know what they don’t like, and what will automatically get you “Google slapped.”
Don’t Wear the Black Hat
Remember how in old movies, the good guys wore white and the bad guys wore black? These days, “black hat” techniques are those shady ways developers use to get better placement on search engines. While some may work for short periods of time, you can guarantee Google will find out and put you back in your place.