If you ever have the good fortune to create a great advertising campaign, you will soon see another agency steal it. This is irritating, but don't let it worry you; nobody has ever built a brand by imitating somebody else's advertising.
David OgilvyThe most important word in the vocabulary of advertising is TEST. If you pretest your product with consumers, and pretest your advertising, you will do well in the marketplace.
David OgilvyThe relationship between a manufacturer and his advertising agency is almost as intimate as the relationship between a patient and his doctor. Make sure that you can life happily with your prospective client before you accept his account.
David Ogilvy