Check out this Website Credibility report from Stanford University.  The compiled 10 guidelines for building and improving the credibility of a web site. The guidelines were based on three years of research that included over 4,500 people.

Here is a sample:

Make it easy to verify the accuracy of the information on your site
You can build web site credibility by providing third-party support (citations, references, source material) for information you present, especially if you link to this evidence. Even if people don’t follow these links, you’ve shown confidence in your material.

Show that there’s a real organization behind your site
Showing that your web site is for a legitimate organization will boost the site’s credibility. The easiest way to do this is by listing a physical address. Other features can also help, such as posting a photo of your offices or listing a membership with the chamber of commerce.

Highlight the expertise in your organization and in the content and services you provide
Do you have experts on your team? Are your contributors or service providers authorities? Be sure to give their credentials. Are you affiliated with a respected organization? Make that clear. Conversely, don’t link to outside sites that are not credible. Your site becomes less credible by association.

Read all to Web Site Credability elements.

Here is a quick look at just a few SEO Best practices.

1. Keyword Research. Are the Keywords you are targeting for (optimizing for) on each page of your site both popular and relevant to searchers?
2. Page Titles. Perhaps the single most important element of on-page SEO, Title tags should be unique on every page and begin with your targeted keywords.
3. Identifying Keywords in your Headlines. The content areas of each page in your site should use H1 Heading tags
4. Content. Assure your content area is keyword rich and of adequate length – 250 words more or less.
5. Text Links within your site. All hyperlink text that point to other internal pages throughout your site should include our optimized keywords
6. 6. Internal Links. Links from your home page should link to your most important secondary pages. Use keyword rich hypertext.
7. Good Housekeeping. Your site should include a privacy policy, as well as a site map with text links. Do you use Yahoo! and Google verified sitemaps? You Should.
8. File Names and Directories Each page of your site should utilize file and directory names that include the targeted keywords you are optimizing for.
9. Linking, Directories and Authority Sites. Is your site Listed in the DMOZ and other useful, relevant authority sites?
10. Content is King. Is your content well written and relevant to the title of your page. The search engines, and more importantly, your audience loves good content. Having great content is the KILLER SEO tactic!