Don't just take my, Yoni's and Ken's word for it: There's ample evidence out there in SEO-blog land regarding the importance of meta tags and aliases and how they contribute to keyword density of your pages and the call-to-action text that shows up in the search engine's themselves.
Witness today's post by Miles Price in Search Engine Journal: 12 Basic On-Site SEO Tactics for Optimized Results.
1. The Meta Keywords, Description and Robots tag — Google used description copy to market your site in its results, treat this as optimized sales copy. Make sure your sitemap.xml page is CONSTANTLY called up to the search engines
2. The Title Tag - The MOST important aspect of on-page SEO, just take our word for it...
5. The URL — The subdirectory folder and page of content should be SEO’d (i.e. http://domain.com/real-estate/real-estate-marketing-ideas.com would fetch a high ranking for a page dedicated to real estate marketing ideas - especially with many highly authoritative, relevant, deep in-bound links)