[xdude]

focus on meta descriptions. the meta description can be used by search engines to show in the snippet, it’s the black piece of text shown beneath the url. the meta description is usually only used when it contains the keyword the searcher was searching for.
some plugins, most specifically the all in one seo plugin, use so called “automated descriptions”. they use the first sentence of a post to fill the meta description by default. that’s not very smart. that first sentence might be an introductory sentence which has hardly anything to do with the subject.

Meta Description is mainly used by Google to display short description about the site in their search result. They no longer give much weight of meta tags like they used to. Now it's mostly about content. But title tag is still important.