The group engage in extreme activities making others pay attention (augmentation principle)
People in groups who repeat the same arguments are dogmatic, decreasing the likelihood of gaining interest from others. Members of the group have to be ready to adapt their views and have valid counterarguments
Explaining the process of change
Hearing something you don't already agree with makes you think deeply about it, especially if the source is all three factors. Minority becomes the majority (snowball effect)