David Ogilvy is one of the most famous ad and copywriters in history. I’m pretty sure the character Don Draper from Mad Men is based on him.
“Big ideas come from the unconscious. This is true in art, in science and in advertising. But your unconscious has to be well informed, or your idea will be irrelevant. Stuff your conscious mind with information, then unhook your rational thought process. You can help this process by going for a long walk, or taking a hot bath, or drinking half a pint of claret.”
David Ogilvy