If they're not too far away then they will use their sense of smell.
But I was sure that I had once read that they are in tune with magnetic fields and can use them to find their way back long distances. So I googled it and found this, it answers your question perfectly
They are actually able to detect GPS satellites and follow the relative coordinates home... just kidding...
I have always wanted to put a small camera on my cats collar and see where she goes all day.. wow cats are amazing animals... sorry for the blurt but I love cats.
i think that cats can sense their way home ie smell, and touch. i think they smell their owners and feel their surroundings as you know animals are very sensitive and can diffrenciate things in their life.
Hope that helps
xx