Reading:
view - Your web site - what you need
Your web site - drawing up a specification
view - What can an 'active' web site do for you?
view - Database-driven websites
view - Hidden 'extras' of e-commerce
view - E-commerce on the cheap

Drawing up a specification

Once you've gone through the 'what you need' page, you should have most of the information to write a specification. You may still need to pin down things like where content and graphics are coming from; whether a database or other 'active' aspects might be useful to you etc.

The following list should be documented in your specification:

1) Existing or proposed domain name
2) A copy of your logo and existing organisation styling if applicable, and any other necessary visual elements
3) A list of sections and subsections for the website, or a block diagram showing a rough plan of the site.
4) Intended audience.
5) Any special features such as 'active' components, database backend, in-house editing ability
6) Any special promotion or site-use intentions (publicised competitions etc) that might have an impact on the site design, or the time frame for completion.

Along with the specification, we would like to have copies of other organisation material such as leaflets, brochures etc, that show us your existing 'look'. And copies of some of the content you want on the site, or summaries.