The Highway Code says that you should only use your fog lamps when the visibility drops below 100m. If you’re not sure when that is, a good rule of thumb is to work out whether you can see the tail lights of the car in front of you. If you can’t, you (and they) should be using rear fog lamps. However, if you can, you probably don’t need them.
Snow does not mean you need to use your main beam headlamps any more or less often than you would normally. You shouldn’t leave them on when you are driving towards or behind other traffic, as it will dazzle those drivers.
If you’re in any doubt about which lights to use, put yourself in the position of other drivers around you. Ask yourself what your car looks like to them, whether they can see you, and whether they might be blinded by any of your lights.
Keep your distance
Cast your mind back to your driving test, and you’ll remember that stopping distances increase in icy conditions. But can you remember by how much?
In actual fact, it can take as much as ten times as long to stop on an icy road as it does on a dry one. If you can, you should increase the distance between you and the car you’re following by about that much.