A hundreds of new websites are being launched every day on different aspects of systems and listed on search engines. So there is a very tough competition between various sites. But only a handful of them survive and get good ranking by doing SEO. Keywords play a very important role in SEO, when search engine bot hit your site it only gets text and from that text it will try to get following details:-

1) Type of business you are doing
2) Type of keywords you are using.

By the business it will put you in a certain kind of category and from the keywords it will calculate how many good keywords you have in the text. By the good keywords I mean that those keywords which are often search on their search engine. So if you put those keywords on your site then search engine will give you a ranking for that because your site has that information what people are looking for.

One important thing that is please dont user one keyword for every search engine because every search engine has a set of rules to give ranking, so one keyword is important for one engine may be it is not good for others.

There in one keyword tool I strongly recommend (www.keywordfindertool.com) that is coming very soon, by that you can search keywords for every search engine... this is the solution for the above problem.