I have to agree that time is going to be key. It takes time to build trust. However there are things you can do to help that trust along in the beginning. We were discussing this in another thread here about how the color blue inspires trust. If you look around you'll see that blue is often the color choice for clothing of salesman and corporate websites.

The words you use on your site can convey trust or lack of it to someone. Make sure everything you say is consistent. Add a privacy policy to your site and add a line near your contact form about how you never give or sell anyone's email address to third parties. Little things like that can go a long way.

Testimonials will definitely help since it shows that other people have placed trust in you and been happy with the results.

A lot of it will come down to time though. The more people can see you deliver on the trust the more the word will spread.