As a client; how to present database needs to perspective designers?

I am preparing to solicit proposals for database/project management software design. I know that the quality of the final product will depend on how clearly and completely I can organize and explain the needs of my dept. to perspective consultants.

Is there a format that is helpful to use for organizing the information the designer will need? Specific types of information they will require? Or perhaps resources online that more or less explain the designer’s point of view and what they are looking for from a client? How detailed should I be during the initial proposal request?

I have found a few articles explaining concepts of good database design, but they are targeted toward designers, not clients. I’d really appreciate any insights this community might have!