Lean Thinking is known as a systematic approach to identify and eliminate waste through continuous improvement, flowing the product at the pull of customer in pursuit of perfection. Indeed, a Lean Transformation is a complex organizational journey, which must emphasize the supremacy of the principles as they emerge from practical tools application. In general, the stages of a Lean journey may span the whole company, not only the production departments. The aim of this chapter is to present the factors enabling or disfavoring the Lean Transformation of a firm, along with the most relevant tools or practices to be applied. The chapter is targeted on manufacturing Small and Medium Enterprises, which can find there a broad set of indications and prescriptions to keep in mind, before starting any Lean project. The empirical research work has been divided into three parallel sections, Lean Manufacturing, Lean Design, and Lean Office, respectively. In every section, the most important issues about Lean Transformation have been investigated through a Delphi study, which was performed by joining the “Lean Community” research project, sponsored by Confindustria Padova, the Federation of Employers of Padova, Italy. Thereby, the study involved 32 manufacturing SMEs in Northeastern Italy, with a proved and excellent experience on Lean Thinking.