There are basically two ways of giving yourself instant credibility:
1. Design of Site
Websites HAVE to look professional. Sure, the occasional cheepy looking one makes it, but they could have done a lot better with a great design. Once you start making revenue, it might be a great idea to invest a pro-webmaster who has a fantastic portfolio to design your site. If you are using wordpress, check out premium themes.
2. Style of Content
Half of great content is content that /acts/ like it's great. I learned this in five years of formal debate. The number one secret to success is to /sound/ like you know what you're talking about. Confidence. Facts. Style. Check out Copyblogger.com for great ways to spiffy up your style.
Hope this helps!