I agree on the tires. The cheapest winter tires are still better than the best all seasons. I've seen several BMW's with all seasons literally unable to move in a flat parking lot. I remember a co-worker with nice wide flat tires, car looked beautiful, but we had to go out and push him into a parking space, otherwise the car just would have sat in the aisle until spring. I said he may want to look at getting narrower taller snows on steelies. He looked at me like I insulted his mother or something...
Also, when the snow fly's play with the DSC if you have it. The point of DSC is to keep the car on course when you think you are a better driver than you actually are. It has saved my a$$ as few times. It's like the car telling me "OK, there's your warning...slow down dude..."
I find the DSC, at least on X3 at low speeds, works against me in the deep stuff. Climbing the driveway thru a foot and a half of snow, with DSC on it is constantly backing off power to one wheel or braking another (which is what it is supposed to do), but the car struggles more. Shut off the DSC, get full power to the wheels and it climbs like a champ. Same thing pulling the boat out in the fall.
Regardless of your set up. Find a empty parking lot or whatever and get comfortable with the car and you'll be fine.