"Getting SMS campaigns right is not simple. The right content, delivered at the right time in the right context, is critical. Adding the right kind of interaction to campaigns can make them more engaging, and increase their power in encouraging positive change. Positive behavior change campaigns should also ideally be measurable - this is never easy, but when your recipients are difficult to access physically, as is often the case with SMS campaigns, this becomes more challenging. This guide seeks to introduce some key points to think about when planning to use SMS for behavioral change campaigning." (Introduction)