Other than your site's page titles, one of the easiest ways to make a huge difference in your organic search results is by perusing an external linking campaign.
The idea is to get as many links as you can from popular websites, with your targeted keyword phrases in the anchor and surrounding text. Ideally, you want to get what are called one-way inbound links. One-way inbound links are links to your site from another website that are non-reciprocal. There is some evidence that search engines even consider the overall topical theme of an external website. Therefore, if you are in real estate, a link from another real estate related site would be worth more than the same link on a non real estate related site.
The number of links you have to your site is called link popularity. In other words, how popular does the rest of the web think your site is. One of Google's key ranking factors is Page Rank which modifies standard link popularity to weigh how much link popularity the page that is linking to you has.
In general, the search engines weigh external links higher than internal links because it is a measure of another's opinion of your site. The theory goes, if your site has valuable and/or unique information then people will link to you. External linking is so important that some search engines will drop you out of their database if they cannot find enough external links to your site.
Another important benefit to external links is that search engine spiders will follow those links to your site. The more often spiders find your site, the faster you will be added to the database, and the quicker any site changes will be updated.