Is the navagation on your site consistent and easy to follow?
Are there pages of your website where people get confused and lost. Are there pages on the website that do not have a link back to the front "splash" page?
Do the users of your website tend to follow paths other than the ones you intended? A "survey" evaluation of your site can identify these types of problems.
Could the website end users easily find what they were looking for? (use an evaluation survey).
How long did it take for users to find what they were looking for? (use an evaluation survey).
Could the end users repeat their searches the next day in any less time? (Use an evaluation survey).
Is the type legible against the background? Are you using enough contrast? Are you using too stark backgrounds and text such as white on black or black on white?
If you're selling products from your site, could the users complete the transactions confidently smoothly without having to go threw too many screens? (Use an evaluation survey).
Are you providing feedback on form submissions to let your end users know that you have received their submissions.
In general, You should try to make your sites efficient enough that visitors can find specific information in the fewest number of clicks as possible. The important thing is to make your most vital content accessible quickly. More specific content that might be buried in your site should be no less accessible, even though it will usually require more clicks to access it.
As your users click through your site, try to give them contextual clues all long the way, so they can see the logical progression of their navigation.
When you view other professional websites such as google or yahoo, watch how those sites often leave bread crumbs, markers, and other clues to help you find your content. Some of the simplest sites that offer good content are often the best.