Park only where directed and as close to the bank as possible. Leave the vehicle in gear. Don't use the handbrake - it could freeze on. Lift the wiper blades off the windscreen. Watch out for other travellers and animals.
High ratio is best, if possible.
Lower the tyre pressure to 140kpa or 20psi. Remember to reinflate your tyres as soon as you're back on hard ground. Stick to any existing wheel tracks - it's a lot easier. Avoid sudden changes in direction or acceleration. Coast to a stop if at all possible.