Most people when they think design think about how a thing looks. This seems to be especially true for websites and over the years I've seen a lot of amateur designers place too much focus on how their sites look instead of their sites function.
Design is really about solving problems. Aesthetics certainly pay their part, but your website has specific goals and your design should help aim to help achieve those goals.
I believe in architect Louis Sullivan's principle that form follows function. Before designing a site think about what it's function is. Why does the site exist and what business goals is it meant to help implement.
Here's an article I found at Smashing Magazine, titled 7 Essential Guidelines for Function Design that offers tips for helping your site design be more functional.
Here are there 7 tips:
More details about each can be found in the article and I'd encourage you to read it. Even if you don't think about the 7 items listed above and ask yourself how well your site accomplishes each.
1. Consider the productís goal.
2. Consider who will be using it.
3. Consider what your audience intends to do with it.
4. Is it clear how to use it?
5. How does your user know itís working?
6. Is it engaging to your users?
7. How does it handle mistakes?