As a person interested in "group influence" it would be well worth anyones while to rent/buy the movie "Mouth to Mouth".
Based on the directors brief experience in Europe as part of cult the story centers around Sherry, a young runaway meets the radical street collective SPARK - Street People Armed with Radical Knowledge - while she is living on the streets of Europe. She travels through the continent in the SPARK van, recruiting members from street gangs and disenfranchised youth at raves and town squares and experiencing the group's giddy thrills as well as its punishing manipulations. Searching for a place to belong where she can still be herself, Sherry thinks she has found this in SPARK, but when her mother comes to find her, Sherry discovers that she must pay a heavy personal price for rebellion. Director, Alison Murray combines drama, suspense and choreographed movement in an intense, stylish and provocative look at youth culture, the struggles of parenthood, and the dark side of nonconformity.
What one can learn about "group influence" from this film is how easy it is to influence people when you offer them a sense of community and a little hope and encouragement.
The formula becomes very clear.
1) treat them as your friend and show interest in them as a person.
2) Act like you know what you're talking about.
3) Give them the idea that they are part of something bigger, a cause.
4) Enforce obedience to the group cause.
You can also learn how easy it is for a group leader to abuse the power that is given him.
All the characters in this movie have SOMETHING in them that we can empathize with, even the abusive cult leader.