The following is a handy list of suggestions towards organising the content of a new site. These steps are useful in deciding how the eventual website will look. However, if this seems unnecessary complicated, you can rely on your designer to interpret your wishes appropriately.
Purpose
Before creating your web site it is helpful to have a clear idea of what you want your site to do, who your target audience is, and what you want to say to them.
Planning
List your main themes (pages?). These will become the foundations of the site structure.
Structure
Knowing what your main pages are - set out an outline "tree" structure of everything else you would like to see.
Home page
The Home page is the first glimpse that people get of your site. Given that the average attention span a casual surfer is willing to spend on a new site is in the region of 20 seconds it is very important to ensure that first impressions count.
Design
If all this seems a bit too much, don't worry, it's the web designer's job to ensure your site is optimised to it's greatest advantage - and that it looks good! The ideas listed here were just to help with the planning.