The other tip not yet mentioned is the one I always hate, because it’s ambiguous (at least to me): “steer into the skid.”
I never knew which way that meant, so, finally driving a car regularly in winter, I tried to work it out. It simply means point back the into the lane if you are fishtailing. Point the wheels in the direction your car is actually moving. This always seemed to me to be quite obvious, so it seemed confusing that the whole “steer into the skin” maxim was non-obvious. But I guess what’s non-obvious is that if you are steering left, it’s likely you will over-steer and start to skid, and so you will need to steer very slightly to the right.
It’s quite possible you will over-correct, so this may take more than one iteration (hence “fishtailing”).
This video was very good:
