Zener Diode for microcontroller pin protection

Hi I want to know how to use zener diode to protect my microcontroller intput pin from Over voltage.

I have an Arduino running at 5V and it has to read analog voltage from a 12V sesnor. So I used a potential divider circuit to convert that 0-12V sensor to 0-5V sensor and hooked it to the Analof pin of Arduino (A0). Everything is working well and I am about to design my PCB. But I wanted to protect the arduino analog pin from getting damaged is the 12V accidently reaches the Arduino pin.

I know that I have to use a zener diode may be 4.7V zener, but I do not know where exactly to use this zener diode also do I need to use a zener resistance as well if yes what value? Is there any other way to protect my pin from over voltage?