My mom taught me the best way to learn how to get out of a "fish tail" is to do "dougnuts" in an empty parking lot. Granted make sure there is no cops around but it really does help.
The only reason my mom is one of the better drivers in the snow around this area is because she is from Colorado and when she was growing up she had at least a foot of snow to drive in...granted that is an ideal snow fall there.
Well,doing doghnuts definitely helps you get a feel for how your car moves when it slides. Actually, when your car fishtails, you should steer into the spin (if your making a left turn, and the rear end fishtails, you would steer to the right, instead of to the left). When you do that, you are basically trying to move the front end in the same direction that the beck end is going, so the back end doesn't keep whipping around the front end. After steering into the turn, there's a point where your wheels will catch again, and you need to steer in the direction you want to go again.
Instead of doing doghnuts, the better way to learn that sort of thing is drifting in parking lots. You drive forward, begin to make a turn, pull the emergency brake, and then try counter steering, like I described above. If you do that successfully, you can have a lot of control over where the car goes. My friends have a habit of drifting around corners when they're driving in town in winter for fun.