I'm convinced that for "small sites" like what most of us have (we're not google or wikipedia), backlinks are the key to getting high search engine rankings. Of course, relevant backlinks matter, too, but the single most important thing is quantity of backlinks.

Here's a strategy I use to get TONS of backlinks to my sites. I call it Backlink Building Wheels.

Step by step:

1. Write an article for an article directory like ezinearticles.com or GoArticles.com (here's a good starter list of article directories). I like goarticles.com because it's quick, easy, and the search engines love it. Place one link in the body that points to a page or post on your site. At the end of this, you'll edit this article to complete the wheel. But for now, just place one.
2. Write another article that is similar to the first one and publish it in a blogger.com blog (free easy setup). In it, place two links – one to the page you want to promote (the SAME page as in #1) and one to the actual article that gets published in #1.
3. Write another article, this time on Live Journal. Two links – one to the same page on your site, the other to the article in #2.
4. Repeat 5-8 times. I use GoArticles.com, blogger, Live Journal, Squidoo, hubpages, and wordpress.com.
5. Go back to #1 and put in another link – this time to the LAST article you posted, thus completing the "Backlink Building Wheel."
6. Using social bookmarking services like ping.fm, promote all of the articles above.

This is a very productive strategy for getting relevant backlinks to your site. It may sound cumbersome, but once you get the hang of it, you can create one of these wheels in less than 15 minutes. Time well-spent for getting quality backlinks, if you ask me.

This strategy works well with other backlink building services such as Angela's Backlinks. Simply use #6 to promote the relevancy of each backlink you get.