The last time I wanted to buy a book from my home computer, I didn't search "books" - I entered "Amazon.com" on my browser. And then I bought a book. My tactic is supported by WebSideStory, reporting that direct navigation had a 4.23% conversion-to-sale rate, compared with 2.3% for search engine clicks.
While we may not be as fortunate to have such a directly recognizable domain name, there are options. Besides an aggressive campaign to put your domain name at top-of-mind with consumers, purchasing a keyword domain name could be the solution. It may be much more expensive at the outset but, over time, you could end up saving loads of money by not having to resort to PPC ads and search engine optimization spending. You could simply redirect traffic from a newly purchased and generic domain name, or completely re-brand your business around the domain name.
Depending on your business, buying a direct navigation domain name could hold be the ticket to saving money and generating higher sales. Consider spending thousands of dollars every month on PPC, versus spending $200,000 once on an instantly recognizable and generic domain name - the long term savings could be astronomical. This strategy is even more prudent considering that applicable domain names continue to disappear over time.
A good place to start is by looking at the correlation between search query volume for the keyword that you are considering as a domain name. You can do that here.