Learning MI does not necessarily require going through one or more training sessions, although it is common for those who are interested to attend a beginning and intermediate workshop (usually 4-6 hours each). Professional development to learn MI can be self-directed using books, observing clips of MI and taking advantage of web resources. It is helpful to go to a workshop that is interactive to maximize learning, where the skills are explained and practiced.
In addition to the authors who are experienced in leading professional development workshops in motivational interviewing for educators, there are trainers all over the world that train practitioners from various fields. The nonprofit organization Motivational Interviewing Network of Trainers has a listing of members who have gone through a training for trainers. Although the skills of MI are consistent from field to field, some trainers are more experienced in working with educators, vulnerable young people or social service settings. Since MI in education is quite new, this organization has not added a category for training in education, the closest being Social Service.