Website optimization starts with keyword selection. This is a very important step as it will partially determine how your visitors will find your website using search engines. The key to keyword optimization is to choose search phrases that are popular among surfers, but not too competitive; this means that you should stay away from single terms and rather target 2 or 3 word search phrases. Studies have shown that an increasing number of individuals are performing multiple keyword searches, which means an increase in competition for even more search terms.
To get an insight as to which search terms are popular, you need a keyword suggestion tool. What these tools do is collect information from a number of different, pre-selected search engines. When searching for the popularity of a keyword, the tools return the keyword as well as variations of it along with the number of searches that have been conducted in the last x number of months or x number of overall searches. Each tool has its individual way of grouping the data; some group single and plural terms, while others keep them separate so examine the results beforehand to assure that the reports are presented in a form that is acceptable to you and makes your keyword selection process easier.
Sumantra Roy of 1stSearchRanking.net goes into detail about which keywords you should optimize for. She has developed a formula, called Keyword Effectiveness Index (KEI) which helps in determining which keywords will yield the best results for your site. To get the formula and learn more about her findings, please read the article available here.