Search optimization, the basics
The best practice is to put the keyword in the page's file name, title, and deion meta tag. (The keyword meta tag, despite the name, is irrelevant to good SEO. It was so overused that search engines generally ignore it now. ) The keyword should also appear in any anchor text on links pointing to the page, and should appear in the body of the page a certain number of times. The number of times a keyword should appear in the body is a delicate and tricky part of search engine optimization; to prevent abuse, search engines change their algorithms frequently, so one year the most SEO friendly percentage of keyword appearances is 10%, then the percentage drops to 6%, then to 4%.