To cripple a cult beyond repair, always follow the money trail.
Cults need food, shelter and clothing like everyone else, and unless they have a wealthy benefactor or they're truly isolated, living in a jungle and growing their own food, that means they need money.
Some cults make money to sustain themselves by legitimate means. The Heaven's Gate cult in San Diego, Calif., had been running a successful Web design business before they committed mass suicide in 1997.
Some cults commit crimes like fraud and tax evasion to help support themselves. They may use deceptive fundraising techniques or require that new recruits make significant financial contributions to support the rest of the cult.
Above all else, life in a totalist cult is typically characterized by tight control.
There is very little freedom in daily life: The leader prescribes what a member can and cannot do for every minute of the day. This includes what food he can eat, what books he can read, whom he can talk to, what he can wear, where he can go and how long he can sleep. The leader makes decisions, and the followers do as they're told.
If cults are unable to acquire items needed for members to live and survive, they are unable to continue.