Individuals and interactions over processes and tools

Working well with others, communicating and interacting, is more important than raw programming talent. A team of average programmers who communicate well are more likely to succeed than a group of superstars who fail to interact as a team.

Robert C. Martin, "Agile Practices", in Agile Software Development:
Principles, Patterns, and Practices, 4.

[...] the quality of the people on a project, and their organization and management, are much more important factors in success than are the tools they use or the technical approaches they take.

Frederick P. Brooks, Jr., "The Mythical Man-Month after 20 Years", in The Mythical Man-Month (Anniversary Ed.), 276.