Meta Tags are statements, visible only to Search Engine Robots, about the nature and subject matter of the page.
The Title Element is of key importance. Think of it as a newspaper headline (or two or three), not an essay. Example:
Smith Wins 2012 Florida Vote | Jones Loses Florida Election
A Title Elements first 65 (or thereabouts) characters are displayed as a headline in Search Engine Results Pages.
Description Meta Tag
Description Meta Tags appear in Search Results beneath the title! Google displays about 160 characters in Search Results, and probably indexes more characters. Don't use a generic phrase, or omit it Description Meta Tag!
Description Tags factor into Google "Quality Scores," impacting Adwords campaign performance.
Title Elements and Description Tags help Google determine unique pages, according to many SEO professionals. Similar pages may be judged unworthy of inclusion in Search Engine Results Pages and/or crawled infrequently. Unique Description content for every page encourages Google to crawl your interior pages more frequently.
The Keywords Meta Tag is unimportant from the perspective of Search Engines results, but in can serve as a comment to individuals revising the web page - everyone changing content will be aware of the targeted keywords for that page. Additionally, it may have some very minor impact on search results. Don't use a generic phrase, or omit it Description Meta Tag!