Keywords is the most important thing to search engine. Keyword is word which searchs the most related word from the site. So you have to use most words which is used in your website.
1. Dont Use long Keyword to search engine.
2. Use those keywords which words are used mostly in website.
3. Use Meta tag in your Websites and Blogs.
if you need more information how to add and what keywords you have to use then search at any search engine like google Yahoo etc.
