There are several things to consider before investing any money in getting a website designed or an existing website redesigned. It is important to have a general plan of how you want the website to work, how the navigation between pages will work etc. As stated on elsewhere on this site, the back button is your enemy. If your pages are not easy to read, navigate or generally friendly to the purpose of the visitor, you will lose them very quickly.
A small amount of time spent thinking about how you want your website can save you a lot of time and money down the road. The major problem for most websites is that they have poor usability. A really good book, that you can quickly read is Don't Make Me Think: A Common Sense Approach to Web Usability, 2nd Edition. It will make you think about your website in a different way.
If your site is not purely an information website, then you want your visitors to do something when they visit your site. How the pages are laid out can make a big difference to whether your visitors do what ever it is. A good introductory book on this topic is Web Design for ROI: Turning Browsers into Buyers & Prospects into Leads
If you want to see some state-of-the-art coded sites check out CSS Zen Garden