It is very difficult to show the right path of devotion in a devotee as they have to give concrete proof. First of all, if you are making any devotee, first of all, you must have complete knowledge of everything.

The mind of a new devotee is still filled with materialistic feelings from the outside. Until he clears those things completely he will not be able to concentrate in one place. So give proper knowledge to that new devotee and explain the essence of the knowledge given by the Acharyas.

Explain to them the real meaning of the Bhagavad Gita. And slowly start bringing them on chanting, after that, they will automatically release the cause of birth in this material world.