How can I get penalized from google?

I write blog post and keyword density is high but not as much
I build forums,web 2.0,profile links to web pages as backlinks

Is there any chances of getting penalty from google.

If you want to get penalized then build a lot of backlinks with exact match anchor text and put the same exact match keyword in the URL, Meta, and H1 tags.

Just kidding, read Google Webmaster Guidelines to get a basic idea about penalties.