If you think optimizing META tags alone will increase search engine positioning, think again. In fact, many engines now ignore meta tags altogether because they often contain spammed content that is not relevant to the page.
Still, meta tags have their uses. They can help you provide descriptions and keywords on pages that for various reasons lack text, such as flash pages and frames pages. They might also boost your page’s relevancy. There are several meta tags, but the most important for search engine indexing are the description and keywords tags.
The description meta tag is especially important since search engines and directories will often use it as the description in their search engine result pages. Thus, people searching will often find the search result to contain your title (as a link) followed by your meta description, so it’s important that it be well-written and entice people to click to your site. The search engines will allow anywhere from 150 to 250 characters in this tag and will chop your description when it hits their allowable limit.
The description tag needs to be a sentence or two that describes exactly what a particular page is about while including important keywords. Remember, this tag is often the description that shows up in the search engine results page,
As for the keywords tag, the best advice is not to worry about it too much. Remember to only put in keywords that can be found in the text of that particular page. Also, don’t repeat any instance of any particular word more than three times. This way you’ll be sure to not inadvertently spam the engines.
One other meta tag worth mentioning is the robots tag. This lets you specify that a particular page should NOT be indexed by a search engine. You should also look into setting up a robots.txt.