I feel this is a repeat of a previous poll...
The answer: It depends.
-Sometimes I have no hands on the wheel, and rest them on my lap ready to take over.
-Sometimes I rest them on my lap and keep my thumb on the wheel in case it does anything stupid, I'll reduce the required reaction time.
-Sometimes I keep my elbow on the armrest, and keep 2 fingers on the wheel (sort of the way I normally drive anyways), but very lightly gripping the steering wheel and sort of resting my hand on the steering wheel as it feels natural to hold the wheel while in the car.