Determine your menu and content for your site by deciding what service, product or type of site your client is needing. Some clients have no idea what they want, it's up to the designer to help the client understand the types of Web sites there are and how to get started.
Clients you're working with usually have a better understanding of their business than you do. You will need your client to provide as much information about what they do as possible -- have them provide types of brochures, business cards, newspaper ads, yellow page ads or anything else you can think of that will help you design and structure their site.
At this point, you may need to hire a copywriter to produce text for the site. If the client does not have this in their budget, then have the client provide text for you based on your guidelines. Some clients already have an idea of what they want. Use what they have and enhance it when necessary.