Summarize the goals of this job. What do you want to achieve? What action do you want the customer to take? Or what do you want them to feel or think?
Who is your target audience? If you build a complete picture of the audience that you must persuade, I can do a better job of tailoring your designs to the audience's needs and concerns.
Some questions to answer: Who are they and where do they live or work? How will they be reached? What issues concern them?
What is the tone of your written copy and your message? What adjectives describe the feeling or approach? What do these adjectives mean to the customer?
What do you want to say? What will the audience remember at the end? What similar messages are competitors using?
Is there a certain visual style you want? Are there visuals in place already or must they be created?
List all elements and their formats/measurements.
When do things need to be done?