Depending on the project. If you want something for print or web made from scratch then I often don’t need anything apart from the information you want depicted (if anything specific). For websites, brochures, general needs include the content (unless I am writing it), images/photos should you have any specific ones to use, logos, and requests or ideas if you have any that you are keen on.
All media you send me should adhere to the submission specifications detailed in the TECH & SPECS ADD LINK outline. I will usually send you a list of the things that are needed to proceed with the project upon acceptance or enquiry.
You also need to have an idea of an end result: what are your expectations? This is extremely important for websites. If you are happy to leave it up to me that is fine, however I will need some information on your goals and needs and can send you some questions that will help define these objectives.