SEO - improve keyword density

I started to study keyword density now, it might help improve my ranking.
Take a look at this article
http://www.aboho.com/forum/showthread.php?t=2355

There are a few catagories the author has shared tips on

• First 25 words
• Hx (heading tags)
• Anchor Text
• Bold and Underlined
• Last Paragraph
• Keyword Weight
• Keyword Density

I will try to practise more and do something on it.