Q. How can I stop sinful thoughts occuring in my mind?
A. You can stop sinful thoughts by loudly chanting the Holy Name of God, Hare Krishna Hare Krishna Krishna Krishna Hare Hare, Hare Rama Hare Rama Rama Rama Hare Hare.
Also it is useful to engage the mind with ideas of how to benefit people instead of ideas of how to exploit them. The best benefit you can offer anyone is to engage them somehow in Krishna’s service.