Along with the title, summaries help users quickly understand whether the page has the information they want.
A summary may be the same as the teaser.
A summary is unique and sufficient to understand the content alone. For example 'find out if you are eligible and apply for a grant' is not sufficient. It needs more detail and the following is better 'find out if you are eligible and apply for a grant to plant trees on farmland'.
Aim for a maximum of 160 characters, this increases the probability search engines display untruncated descriptions.
Summaries end with a full stop.
Summaries are information not already provided by the title. They contain the next most important information about the document.
Use the language of our users. Use keyword tools to optimise your language for search.