Using Meta Tags
When you search for a site in Google, you’ll see a short snippet of content under the page link. To control this, you can customize your meta description tag for the page. Similarly, you can also add keywords to your tag to tell search engines what your site is about. Although that is good practice, Google has recently announced that they do not crawl the keywords tag anymore.
A good few years ago the keywords used to be important as search engines had less ways to determine what a site is about. Now that technology is so advanced, search engines have better ways of determining rankings and relevance.
There is no ideal way for an automated description. The best descriptions are hand written. Using a SEO plug-in will help in placing and character count for a meta description.