Usually to start a new project I will need:
1. Explanatory text.
Of course I need some written details about what you would like to capture in an image. It should not be a complicate, extensive or too technical text. It must be a checklist, to ensure that not a single detail is forgotten. You can include anything that you really think that is important at both, technical and visual, levels.
2.  Supporting Images.
Supporting images are essential to clearly and easily define ideas from the very beginning. Probably you will find schemes directly related or linkable to your idea. Moreover, it is quite likely that you already have images related to the same topic.
3. Preliminary sketch.
Once the concepts are clearly defined, I need a sketch of the idea that you have in mind. You should provide me a draft, but do not worry! The required sketch could be a very simple design that will help us to start working. It is going to be used as a reference, so it has not to be perfect.