Exclusive Affiliate Websites: If your site has no generated content and is based on affiliate programs, you will be penalized by Google.
OOP Over Optimization Penalty: Having a new site over-optimized. Your optimizations should be gradual, not sudden.
Bad links: Having links to penalized sites.
Poison Keywords: Make sure you don’t have words related to pornography, viagra, etc.
Excessive crosslinking: Do not link excessively to your own sites hosted on the same hosting.
Copyright: Don’t copy the content, generate it! Google only accepts on average 25% of the content as duplicate.
Keyword Stuffing: Do not overuse your main keywords. A Keyword Density higher than 10% can be penalized.
Re-editing your content: You can be penalized if you modify your content permanently, remember to add content, not replace it.
Dynamic pages: Do not use excessively long URLs with ID.
Flash: The more flash we use, the less content we offer Google to position us.
iFrames: Do not use! They are not read, not linked, not indexed… no anything!
Invisible text: It is a Black Hat technique that some years ago gave results. Today Google easily realizes it and penalizes it.
Traffic metrics: Try not to have very high bounce rates, it is a highly valued metric today, as Google relies heavily on it to value your content.
Buy Links: Google identifies which are the sites that sell links. If you buy one of those “great offers” that arrive in your email inbox, be aware that Google will not value it.
Accelerated growth of links: if the number of links to your site grows in an accelerated way, Google takes it as something abnormal and you will be penalized. Try to grow the number of links in a natural way.
Server: Even if it costs a few bucks more, it is important to have a server that does not crash regularly.
Massive 302 redirects: If you have 2 or 3 302 redirects it is something natural if you have a few more it is doubtful, but if you have many more Google takes it as something unnatural and you will be penalized without a doubt.