Use of color and fonts again has a large impact on the 'look and feel' of the site. Choose these elements carefully. I am usually not only irritated by this but also inclined to never return. Make sure that as much information as possible is made available on your Web site. I have yet to see a site that had too much information.
Consistency is again important.
Spend time navigating your site. Ask the opinion of others. If you use graphics for navigation, provide alternate text navigation. One simple technique I particularly like is the use of small text navigation at the bottom of each page. I usually include top level links, links to other pages in a section of the site, and an email link.