What is the best way to promote behavioral changes?

Behavioral Therapy. Behavior is a function of its consequence. Most behavior is maintained if it is positively reinforced and extinguished with negative consequences. The art of promoting change is the application of these principals to the specific person and circumstances.
Align with values. One way to promote change is to determine how alternative choices align with personal values and what is most important to someone. This is often helpful to increase perceived value for initiating a change.