the power of links
While it's important to make sure all the your on-page factors (meta tags, keyword density, etc.) are taken care of, incoming links are currently the single most important way to rank well for a term in the major search engines. As an example, go to Google and search the words "click here." You'll see that the page for downloading the Adobe Reader is listed #1. A few things to note are:
1. The word "click here" isn't in the page title
2. The word "click here" isn't in the URL of the website.
3. The word "click here" isn't even in the description listed by Google.
Now, click on the listing in Google and check out the actual webpage. The words "click here" aren't even on the webpage, anywhere! The main reason that adobe.com is ranked #1 for the keyword "click here" is because there are many websites linking to adobe.com using the keywords "click here" in the text of the links pointing to adobe.com, and many of those websites are high quality.
Link building can be one of the most difficult, time consuming aspects of an SEO program, but the results are also the most powerful. Getting links from high quality websites with keywords you want to rank for in the anchor text should be at the top of your SEO to-do list.
As a side note, this also shows the importance of using keywords in your link text (also called "anchor text"). When refering to other pages of your site, instead of saying "click here," try to use more descriptive words, preferably keywords you want to rank for. Remember, every link out there counts, including the ones on your own site.