Here's my tip that was successful last winter- We have a heat lamp in our coop for the winter, but the water bowl inside still managed to freeze. Our solution was to screw a light bulb (not sure on the watts) to the floor, then place a flower pot over it, completely covering the light bulb. When it was turned on, it was warm to the touch. Warm enough to keep the water from freezing over if the bowl was placed on top of the flowerpot. Last year we were beginners, and our plan still had some flaws. The chickens would knock over the water bowl, getting cold water everywhere. We also quickly realized our coop was drafty, and the walls inside got wet every time it rained or snowed heavily. This year we plan on improving our water-heater by screwing the water bowl into the flower pot. Hopefully the water will not leak through. We are also going to insulate the coop to hold in the warm air we produce through the heat lamp, flower pot/light bulb, and chicken body heat.
This is unrelated to keeping the coop warm, but for chickens and ducks, shovel paths in the snow for them to walk around in. It makes them want to go outside more and they get a chance to get fresh air. Just supervise them and make sure no one gets too cold outside.