A web designer offers HTML and graphics services and designs visually focused web pages. The difference between web design and web development is that a web developer usually has more back-end programming skills and a web designer is more focused on the look and feel of a site. A good web designer will help you organize the information for your web site and develop navigation and layout.
Web designers usually charge based on experience, designers with less experience may save you money but more experience designers will almost always deliver a higher quality product. Before you choose a web designer you should review other web design projects they have worked on, and contact past clients if possible. Some designers charge per project, some per page and some per hour. Make sure you have defined the requirements for your web project and both of you have an understanding in writing of what is expected.