Today, optics and photonics technologies have an important impact on nearly every area of our lives, covering a wide range of applications in science and industry. Photonics has been recognized as a Key Enabling Technology (KET) by the European Commission. However, despite its importance photonics is still not well-known to a majority of people. To challenge this general lack of awareness about photonics, the European Commission funded the Photonics4All outreach project which was designed to promote photonics and light-based technologies to young people, entrepreneurs and the general public throughout the EU. Between January 2015 and December 2016, 9 Photonics4All project partners developed a set of promotional outreach tools which were used successfully during a variety of different outreach activities with over 400,000 people. The project aimed to engage the target groups with photonics and photonics applications, and inspire a greater interest in photonics amongst all those taking part. This handbook summarizes our best practices in promoting photonics and light-based technologies to young people. The handbook is aimed at all those public and private organizations willing to organize outreach activities for young people, and should be useful to newcomers or those more experienced in science communication.