The learning benefits deriving from the use of mobile technologies in in-field research and professional training have been demonstrated by a number of initiatives worldwide. Because learning can occur in highly variable places and conditions, the choice of mobile device and an accurate analysis of the target users are essential during the design phase of Mobile Learning applications, to identify the user scenarios and various possible experiences deriving from use of the system. The present work reconstructs previous experiences in the field of designing contents for Mobile Learning, with the aim of gleaning clear guidelines for designing and implementing highly efficacious, usable contents and courses for mobile devices. These guidelines were applied to create a course on the work of Caravaggio, to be studied using a handheld device.