One of the most important things you can to on your site for SEO is to have a well defined and optimized site structure. Can you find everything on your site without searching? Try getting to everything on your site using only a mouse. Remember that search bots don’t do searches. This is a problem that many large sites have (including WorldVitalRecords.com. FamilyLink.com is better). You want to build your site horizontally not vertically. Avoid content silos and use content themes to organize your site. One great tip is to use a different sitemap for each section of your site. Sitemaps greatly help the crawlability of any site.
Scott Polk is in charge of SEO at Edmunds.com. They do very well in the search engines and they have reaped many benefits from organic search. It was very interesting that EVERY employee who works on the site gets SEO training. Plus every project on the site gets reviewed by the SEO team. They also have this idea of attaching personal revenue to each employee and organic search is part of that. I LOVE this idea. I have never seen a company so committed to SEO.
Another great SEO feature is the “Share/tag this page” link that HP.com uses on some of their pages. These link pop up a box with many social media tagging options like in this image.

This is a great way to get incoming links to many pages of your site. I could also see the email this to a friend option and print options tied into a page like this.
Many large sites have a problem with creating xml sitemaps. I have tried to build mine using data right form the database but don’t feel like this is really getting all the pages (plus some of the pages are behind the member login). But large sites are too hard to crawl with an external crawler. I asked this question to Mr. Polk and he told me that Edmunds.com uses xml sitemaps and have like 160 of them daisy chained together. But Tanyan Vaugh the SEO director at HP said they do not even try to build sitemap files for their site. Bruce Clay said that he uses xml sitemaps whenever he can. But if you cant build a complete one, he suggested at least getting all your major pages in the file. He also suggested putting pages that are having trouble getting indexed in the sitemap file. Sounds like practical sound advice. I like Bruce (btw, check out his coverage of PubCon on his blog. He must be recording it and getting it transcribed because almost every word is there. Amazing!).