How to optimize or write description tag for search engines

What is a Meta Description?

Meta description tags, while not important to search engine rankings, are extremely important in gaining user click-through from SERPs. Meta descriptions are HTML attributes that provide concise explanations of the contents of web pages. Meta descriptions are commonly used on search engine result pages (SERPs) to display preview snippets for a given page.
The meta description should employ the keywords intelligently, but also create a compelling description that a searcher will want to click.

Writing meta description for SEO

Write Compelling Ad Copy
The meta description tag serves the function of advertising copy. It draws readers to a website from the SERP and thus, is an extremely important part of search marketing. Crafting a readable, compelling description using important keywords can improve the click-through rate for a given webpage. To maximize click-through rates on search engine result pages, it's important to note that Google and other search engines bold keywords in the description when they match search queries.

Recommended Length
Meta descriptions can be any length, but search engines generally truncate snippets longer than 160 characters. It is best to keep meta descriptions between 150 and 160 characters.

Avoid Duplicate Meta Description Tags
As with title tags, it is important that meta descriptions on each page be unique. One way to combat duplicate meta descriptions is to create a dynamic and programmatic way to make unique meta descriptions for automated pages.

Not a Google Ranking Factor
Google announced in September of 2009 that neither meta descriptions nor meta keywords factor into Google's ranking algorithms for web search. Google uses meta descriptions to return results when searchers use advanced search operators to match meta tag content, as well as to pull preview snippets on search result pages, but it's important to note that meta descriptions do not to influence Google's ranking algorithms for normal web search.

Quotes Cut Off Descriptions
Any time quotes are used in a meta description, Google cuts off the description. To prevent meta descriptions from being cut off, it's best to remove all non-alphanumeric characters from meta descriptions. If quotation marks are important in your meta description, you can change them to single quotes rather than double quotes to prevent truncation.

Meta Description Should Include a Call to Action
Now comes the fun part…
Remember, your title tags and meta descriptions aren’t just fields that you’re optimizing in the hopes of receiving some nebulous SEO boost. Instead, these fields form your snippet in the natural search results, which means that they must be written to be as compelling as possible!
Imagine encountering the two following snippets in the SERPs:

“How to Build Links in 2013

This article talks about link building techniques that will work well in 2013, including email link prospecting, social media marketing and content marketing.”

Versus

“31 Ways to Easily Attract Backlinks in 2013

Are you using dated link building practices that could be harming your brand? Find out how to effortlessly
build links using these 2013-approved techniques.”

I probably don’t even need to ask which of these articles you’d rather read, right?
In a way, writing good meta descriptions draws on the principles of copywriting as much as it does SEO best practices. This can take practice, but the reward is a higher click-through rate, increased natural search traffic to your website and potentially higher SERPs rankings if—as some SEO experts believe—it’s true that your overall CTR contributes in some small way to your snippet’s placement in the natural search listings.

If you aren’t yet an expert copywriter, consider the following guidelines when it comes to crafting your title tags and meta descriptions:
• Add a call to action. Asking people to do something (as in the case of “Find out how” in the example above) often results in readers taking the action you’ve requested. Other possible calls to action for your meta descriptions include “Discover how,” “Read more about,” “Click here,” or other related variation.
• Use cliffhangers. The first meta description show above gives everything away, that is, there’s no real reason for the reader to click through to read the article, as its content is given away by the snippet. Instead, use cliffhangers in your meta descriptions to encourage viewers to click through for the full story.
• Write your tags for yourself. Once you’ve come up with a possible meta tag, ask yourself, “Would I click through based on this information?” If your tags don’t yet seem compelling, rewrite them until you come up with something more enticing.

Don’t forget, you can always test out and refine the effectiveness of your meta tag content by changing the information stored in these web page fields periodically. If you notice a spike in natural search traffic upon making a change, it’s possible that you’ve hit on a winning combination of meta tag text.