Basic Keyword Optimization

Keyword Density

Search Engines prioritize the web page based on the keyword repetition excluding the stop words (the, an, and, etc). Consider particular keyword is repeated 10 times within 100 indexing words where the keyword density is 10% for the web page.

There are plenty of online SEO tools available to measure the keyword density for a particular page or paragraph. These tools will measure the keyword or phrase repetitions in percentage compared to the total number of words appear in a page or paragraph. Below are some good quality tools to measure:

http://www.seochat.com/seo-tools/keyword-density/
http://www.articleunderground.com/webmaster/keyword-density-tool.html

Keyword Prominence

Keyword Prominence refers to the placement of keywords or key phrase within the web page. Search engine bots consider about the keyword placement, so placing the targeted keyword at the beginning of the content in title tags, Meta tags, etc… will give more weight to that specific word or phrase. Normally search engines begin indexing from top left of the page to the bottom, hence including the keyword at the top will help to enhance the website listing position.

Following tool calculate keyword prominence:

http://www.ranks.nl/tools/spider.html

Keyword Proximity

To improve search relevancy, avoid stop words between the key phrases. Normally stop words will be appearing within the targeted key phrase for a specific page which may break down your effort sometimes. It begins from the page title, thus make sure to use phrase proximity sensibly. After all, the top of the page usually tells what you to read about.

Following tool calculate keyword proximity:

http://www.ranks.nl/tools/proximity.html

Also, get more information from SEO Help.