• Differentiate the descriptions for different pages. Using identical or similar descriptions on every page of a site isn't very helpful when individual pages appear in the web results. In these cases we're less likely to display the boilerplate text. Wherever possible, create descriptions that accurately describe the specific page. Use site-level descriptions on the main home page or other aggregation pages, and use page-level descriptions everywhere else. If you don't have time to create a description for every single page, try to prioritize your content: At the very least, create a description for the critical URLs like your home page and popular pages.
• Include clearly tagged facts in the description. The meta description doesn't just have to be in sentence format; it's also a great place to include structured data about the page. For example, news or blog postings can list the author, date of publication, or byline information. This can give potential visitors very relevant information that might not be displayed in the snippet otherwise. Similarly, product pages might have the key bits of information - price, age, manufacturer - scattered throughout a page. A good meta description can bring all this data together. For example, the following meta description provides detailed information about a book.
<meta name="Description" content="Author: A.N. Author,
Illustrator: P. Picture, Category: Books, Price: $17.99,
Length: 784 pages">
In this example, information is clearly tagged and separated.
• Programmatically generate descriptions. For some sites, like news media sources, generating an accurate and unique description for each page is easy: since each article is hand-written, it takes minimal effort to also add a one-sentence description. For larger database-driven sites, like product aggregators, hand-written descriptions can be impossible. In the latter case, however, programmatic generation of the descriptions can be appropriate and are encouraged. Good descriptions are human-readable and diverse, as we talked about in the first point above. The page-specific data we mentioned in the second point is a good candidate for programmatic generation. Keep in mind that meta descriptions comprised of long strings of keywords don't give users a clear idea of the page's content, and are less likely to be displayed in place of a regular snippet.
• Use quality descriptions. Finally, make sure your descriptions are truly descriptive. Because the meta descriptions aren't displayed in the pages the user sees, it's easy to let this content slide. But high-quality descriptions can be displayed in Google's search results, and can go a long way to improving the quality and quantity of your search traffic.