The tires with the most tread should go on the rear.
September 14th, 2015
Tire manufacturers and safety organizations recommend that the better set of tires go on the back, even on a front-wheel-drive car. Putting tires with new tread on the front would help get you started well in the snow. But worn-out tires on the rear could cause the rear end to slide out when turning or stopping.
Because of the ability to steer the front tires, there is a better chance of maintaining control of the car if the front wheels slide than if the rear wheels slide. Once the back end starts to slide, it's a lot harder to control the car, and could result in an accident.
A single new tire should be paired on the rear axle with the tire having the most tread depth of the other three.
Of course, having four good tires is best.