Things to know before working on projects:

1. Project timeline (i.e. template/interface=0 week(s), revisions=0 week(s), etc.)
2. Payment method and schedule
3. Delivery date
4. Delivery method

For most websites, I have them fill in a brief for the site so we understand the expectations, on both ends. Here's a sample of a creative brief. (PDF) I also use a site plan template.