This term refers to the frequency of your keyword versus the total number of words on the page. Although the optimal keyword density varies depending on who you ask, most experts recommend you keep this below 3-7%. If your article or page is, 100 words long, your keyword should not be present more than 7 times. You can check your keyword density using SEO software or on many free sites online.
Relevant Links
Your goal is not only to build up a quantity of links to your website, but that they be links from related and relevant sites topically. You want sites that are similar in theme to link to your site. Though search engines do value the quantity of sites linking to you, they especially weigh the relevancy and perceived quality of those sites. So be observant on both these counts. Otherwise search engines could end up lowering your rank instead of raising it. One of the best ways to build relevant links is by writing articles and submitting them to article directories.
Headers
There is a better alternative to just dressing up your headlines by making them bolder and bigger which will be more effective in drawing eyeballs. Try and use headers. H1, H2, H3 and similar headers are not only helpful in making titles, subheading etc. more prominent, they can also change headline size according to their position in the article. Be aware of certain facts about using headers though. The keyword in your H1 header will be viewed as being of prime importance by search engines, so don't place more than one H1 header on a single web page. It's not technically wise to do so. More than one H2 or H3 headers are OK. You should make an attempt at getting to H6 headers although most websites only utilize up to header H3.
Original Content
No doubt about it. Search engines and surfers love original content. Since search engines store pages visited, content which has been simply lifted from another site will be identified as stolen and will not increase your search rank. Although it might improve a bit due to being more content-heavy, it's not a risk worth taking when you could get far better results using self-written, original content. Quality, original content will always be valued.
