Here are some examples:
* Deter someone from crime: The police presence was intended to deter criminals from entering the area.
* Deter someone from a bad habit: The doctor's warning about the risks of smoking helped to deter her from starting.
* Deter someone from a risky action: The high price of the ticket deterred many people from going to the concert.
In essence, "deter" implies creating a barrier or obstacle that makes someone less likely to take a specific action.