Another excellent guide is Google’s “Search Engine Optimization Starter Guide.” This is a free PDF download that covers basic tips that Google provides to its own employees on how to get listed. You’ll find it here.
Also well worth checking out is SEOmoz’s “Beginner’s Guide To SEO,” which you’ll find here, and the SEO Success Pyramid from Small Business Search Marketing.
There are also a variety of print books you might consider. Here’s our review of some newer books: A Roundup Of Best SEO Books.