Another important Metatag is the Meta Description
The Meta Description allows you to describe the content of a specific page, but with more detail. It is especially useful as it allows the search engines to include a summary of a particular page in their search results. You can try this by doing a search on any term in Google & you will see that the content of the Meta Description will appear on the 2nd & 3rd lines of each listing in plain text.
As a guide try to use around 20 — 30 words, but limit it to no more than 180 characters in total which includes spaces. Try to make it read naturally & remember to customise each one so that they reflect the content of the particular page that you are on.
To get an example of the html for the Meta Description please go to: http://www.pickaweb.co.uk/blog/uk-web-hosting/on-page-seo-meta-description/
You can watch this video also at the source.