Logos, akin to the first word in a conversation between two people, are the best introduction to a company's purpose and standing.

Michael Bierut is a partner in the New York office of the international design consultancy Pentagram, where is work includes brand identity, book design, packaging, and environmental graphics. He is a senior critic in graphic design at the Yale School of Art and the cofounder of the Design Observer website. A book on this work, "How to use graphic design to sell things, explain things, make things look better, make people laugh, make people cry, and (every once in a while) change the world," will be published this fall by Thames & Hudson and Harper Design.