The idea for this text stemmed from the fruitful experience gathered during the training course of 9 Nigerian university students organized in Naples from 3 to 18 September 2008 by the team of Fondazione IDIS-Città della Scienza under the project Science Centre Owerri. The training course turned out to be not only an educational opportunity to acquire knowledge and skills for these students, but also a real and practical tool that later led to the realization of the first Science Festival of Owerri in Nigeria in May 2009. This in turn sparked the idea of creating a highly practical handbook for those who want to face the challenge of developing new projects for the dissemination and socialization of science in developing countries. In these countries, the role of scientific education and training in schools is not sufficient to arouse scientific curiosity among young people and make the population aware of the importance of scientific knowledge in everyday life. Moreover science and technology are indispensable tools for people's empowerment and should be supported with actions that encourage curiosity about science and the intelligent use of technology to bridge the divide with developed countries. It is therefore necessary to set up activities that are carefully targeted to promote and communicate science. The text has been designed as a practical guide to be used in a variety of contexts: scientific events or more structured science festivals, training, the creation of scientific cultural associations, and the development of new science centres. Besides being an excellent tool for training and supporting the design and planning phases, the manual can also be used as a reference work for institutions and local cultural services which have to select projects of this type.