These tips are from Yahoo! Search on how to include META tags, keywords and descriptions in your articles such that your web pages rank high in organic search results:
<title>How can I add meta tags to my pages? – Yahoo! Small Business Help</title>
<meta name="keywords" content="cookies, shortbread, baking, baked goods">
<meta name="description" content="The best cookies and other baked goodies online">
Think about your audience: Which terms would your customers use to find your site? If you’re not sure, ask your friends, family, and coworkers for ideas.
Include variations: People will search for your site using all sorts of search terms, including plurals, misspellings, and synonyms. Be sure to consider these when choosing your keywords.
Look at your competition: If you’re having trouble thinking of search terms, take a look at competitors’ sites. Which keywords are they using? Do they include terms you’re missing?
Remember the basics: Enter your keywords in order of importance, and be sure to use keywords that actually appear in your page content. Don’t repeat keywords more than twice (and not consecutively!), separate your keywords with commas, and keep the list to under 256 characters.
Be specific: Because there’s so much competition for general keywords, you’ll need to choose specific phrases to set yourself apart. For example, if you choose shoes as your keyword, you’ll never get good results — it’s far too broad. Instead choose terms or phrases like women’s patent leather high heels or canvas basketball sneakers san francisco. The more specific your keywords, the more targeted your traffic.
Page Description Meta Tag: The description text should be readable and interesting, and also features one or two keywords that appear in the corresponding page. Be sure your description doesn’t exceed 256 characters. Be sure to include one or two keywords and, if possible, place these near the beginning of your description.
Source: Yahoo Small Business