Meta description tags does not target search engine optimization (SEO) directly, but the message in them can attract interested visitors to your website or blog. Meta description tags are used as the descriptions on the Google search engine result pages, so they have to be compelling. These tags should be relevant and unique for every page on your website and blog.
On the search engine result pages, the title tag serves as the title for each search result. The meta description serves as the body below the title. When no meta description tag exist on the page, a snippet of relevant content/text is pulled from the page. This is automatically done by Google.
The content of the meta description should never exceed 160 characters. Here’s a couple of tips that can help you optimize your meta description tags.
Meta description optimization tips
Length: The length of your meta descriptions should never be longer than 160 characters. The reason for this is that on desktop search, Google doesn’t display more than 160 characters on the description of the results.
Competition: Before you start writing your descriptions, look at what your competition is writing. Get an idea of what messages they are using. Write your descriptions so that you can stand out and be better than they are.
Relevance: Every page on your website and blog should have its own optimized description that describes the content of the page. Make sure they are compelling to draw in interested readers.
Advertising: The main purpose with the meta description tag is to encourage interested people to click on the result on Google and then visit your website or blog page. Include a CTA (call to action) in your meta descriptions to get people to click through to your website. One technique that works is to include your phone number to encourage people to contact you. People will then be able to call you directly from the search engine without visiting your website.
http://wsi4all.co.za/index.php/seo/: Meta descriptions does not affect your seo rankings directly, they should be crafted with the sole purpose of getting people to click through to your content. See your meta descriptions as more about the conversation than SEO directly.