Before jumping into newer Next-Generation State and Gate or Agile/Lean project management practices it is important to recognize older practices that are both great references and the building blocks for newer practices to build upon. The work of Steele in the book Managing Technology and Robert Szakonyi in the book How to Successfully Keep R&D projects on Track are both worth reading for someone interested in building their own solid foundation of issues and solutions to managing technical projects.
The State and Gate process was developed because the previous method of developing new products was typically linear and handed from functional silo to functional silo until the project was completed. This created high costs and little if any iterative learning. A sample process from a large chemical company is shown in the “NPD Process Prior to Stage and Gate Methodologies” figure.