The meta keywords tag allows you to provide additional text for crawler-based search engines to index along with your body copy. How does this help you? Well, for most major crawlers, it doesn't. That's because most crawlers now ignore the tag.

For best results, select 12 of the most popular and relevant keywords to that particular page, ideally keyword phrases of 2 to 3 words, separated by a comma. Ensure that the keywords you use are located in the title, description and content of the page. If they are not, DO NOT add extra words, otherwise the theme of your page will be watered down. The ordering also plays a role, make sure you order the keywords in order of importance. The 1st being the most important.