Search engines; on the basis of your key words index your site. When a search engine sends a spider to your web site, it determines that pages keywords by counting the words on the web page it is visiting. The words that appear most frequently are considered most significant.

Always be sure to research the key phrases you intend on using. Find out what key phrases Internet users most often employ to find your or your competitor’s site. There is no point optimizing your site for "IT career" if everyone types in "Oracle jobs" or “ IBM jobs”.

Keyword Optimization

Keyword optimization, the art of choosing the correct keywords, is one of the most important things related to search engine optimization. In fact it is the first step in website content development.

People generally use key phrases while searching for products or services in search engines, so while preparing the content for a particular web page it is important to select those one or two particular words as theme for the page. It is important to create distinct list of keywords for each page. Around 20 keywords can be short listed per theme and similarities should be avoided. It is however best to downplay the most competitive keywords as many websites would be targeting them. Also it makes sense to target spelling mistakes

There are 2 sites, which offer keyword suggestion tools:

http://inventory.overture.com/d/searchinventory/suggestion/

http://www.wordtracker.com/

The overall process would be:

Add keywords into key tags and attributes, and mix well.

The keyword density is useful for helping achieve optimum words for a set of key terms/keywords. Keyword density is important since search engines use this information to categorize a site's theme, and to determine which terms this site is relevant to -- the perfect keyword density will help archive higher search engine positions.