A typical search results page can be quite revealing - highlighting three important areas of a page, and perhaps the two most important areas of content to optimise:
One key factor to keep in mind is that users see these items before they choose whether or not to click on your listing. Matching users' keywords while being 'click friendly' is key.
It's also worth keeping in mind that this text is displayed on Google's site - not your own. For this reason, writing from a third-person perspective is usually more effective, and you should take care to make sure the text makes sense when it appears away from the context of your site.