Most bloggers grow ambitious in promoting their blog and sometimes get penalized by google search engine.A penalized blog is no longer displayed in top search pages and soon you will find diminished web traffic. Here I have mentioned few common mistakes of bloggers that attracts google's penalty.
Excessive meta keywords
Using more than five keywords in meta data is some times treated as manipulative act to gain SEO by google. So, its better to keep it under four.
It is a bad idea to make a article with little information appear really elaborate and exhaustive . Google instantly penalizes such blogs.
Though your blog has really useful content, you should not boast your blog with too many links on You tube videos and other sites that allow comments. Too much of back links from comments is treated as SEO manipulating act, may attract penality.
Content scraping and duplication:
Most of the bloggers might have good intention to make their posts content rich, but scraping content from other sites is not liked by google. So, its better to refer books rather than sites for generating rich content for your blogs. Before posting it is always better to check your content for duplication using Plag spotter or copy scape tracking sites.
You may be genuine but others may not. Your post content may instantly copied and published by other bloggers. It is always better practice to disable right click till your post is indexed by google. Once you find your new post indexed in google web master tools, you can enable it. See disabling right click on this blog.
Back links from other language sites
If your blog is pointed through back links from sites using other languages, google treats your blog is less useful and may demote in page ranks. So, its better to procure back links from healthy blogs and sites with similar language and content. Avoid swapping links with other bloggers, it is treated as an act to manipulate SEO.
Hosting too many advertorials
Displaying too many ads on your blog in the view of generating revenue is not good idea. Too many ad units dominates the content and gives google a opinion of suspicious promoting activity.